WASHINGTON — When Thabit Pulak, 18, visited his grandparents in Bangladesh two years ago, he noticed something alarming. One of their neighbors had a new skin problem. The skin was discolored and hard. It was a telltale symptom of arsenicosis, or prolonged arsenic poisoning. The source: Many neighborhood drinking water wells contained arsenic.
The naturally occurring element taints the water in many parts of the world. People who drink this water can develop skin disease or cancers.
Thabit sampled well water near his grandparents’ home and found some contained arsenic levels of up to 500 parts per billion (ppb). The World Health Organization guidelines state that arsenic concentrations higher than 50 micrograms per liter of water, or 50 ppb, may be unsafe to drink.A senior at Richardson High School in Texas, Thabit knew filters exist to remove arsenic from water. “But the filters are around $60 to $70,” he says. That would amount to a couple of months earnings for most people in Bangladesh. So the teen decided he design a new filter, one that people in developing countries could easily afford — and perhaps even make themselves.
He showcased the filter and his new and inexpensive test for arsenic, this week, at the 2014 Intel Science Talent Search in Washington, D.C. The competition for high-school seniors is run by Society for Science & the Public. Every year it brings together 40 teens to share the results of their research projects with the public. Many projects have tackled real-world problems, such as disease or pollution.
Thabit’s filter is a roughly 60 centimeter (2 feet) long, 12.7 centimeter (or 5 inch) wide piece of PVC plastic pipe with a cap at the bottom. A tube attached near the bottom of the filter allows water to flow out. Inside the pipe is a mix of clean sand and homemade iron nanoparticles. Sand filters are one of the most common methods to filter water for drinking, and iron particles are used in arsenic filters currently on the market. When water is poured into the pipe, arsenic binds to the iron particles. The sand helps to clean out other impurities.
So far, the new filter has always been able to reduce naturally high arsenic levels in water to below 50 ppb. That’s a level that international guidelines suggest would be acceptable to drink.
Thabit created the low-cost filter in his home kitchen. He tested it on grape juice, which contains trace amounts of arsenic. After a run through his filter, the arsenic levels of the grape juice were lower than before.
He has even made his own nanoparticles out of rust and soap fat. He heated the soap and extracted the fat. Then he cooked the rust in the fat. Over time, the rust breaks up into tiny pieces. These small bits have a higher surface area, making more of the iron available to grab onto and hold arsenic.
This iron mixture also forms the basis for a new test strip to scout for arsenic in drinking water. Thabit dips a bit of paper into the nanoparticles. Then he measures how well the wet strip conducts electricity — both before and after it’s exposed to water that might contain arsenic. The iron bits bind any arsenic in the water to the test strip. That will boost its conductivity. “If there’s a 10 percent [increase] in conductivity,” Thabit explains, “then the water is usually dangerous.”
Currently, the teen is testing the filter at home in Texas and in Bangladesh, to make sure that it will work well during repeated use. He’s also recruited young volunteers in Bangladesh to try out the filters on their water and then send him data on how well they work.
Finally, Thabit is putting the directions to make his new filter and arsenic test strips on the Internet. Anyone can download them for free. That way anyone can build these and improve upon them. “My main goal,” the teen says of his technology, “is to make it affordable and keep it affordable.” If all works out well, such low-cost filters could bring safe drinking water to more people.
arsenic A highly poisonous metallic element. It occurs in three chemically different forms, which also vary by color (yellow, black and gray). The brittle, crystalline (gray) form is the most common. Some manufacturers tap its toxicity by adding it to insecticides.
arsenicosis The poisoning that results from chronic exposure to arsenic, usually through air or drinking water. Arsenic can cause skin disorders, reproductive problems, cancers and diseases of the blood vessels.
bacterium (plural bacteria) A single-celled organism forming one of the three domains of life. These dwell nearly everywhere on Earth, from the bottom of the sea to inside animals.
conductive Able to carry an electric current.
conductor (in physics and engineering) A material through which an electrical current can flow.
electric current The flow of electricity along a given path.
nanoparticle A small particle whose cross-section or length runs only a few billionths of a meter.
parts per (million, billion or trillion) A measurement of extremely small concentrations of one chemical dissolved in another. For example, a solution of 300 parts per billion of sodium in water would mean that there are 300 sodium atoms for every billion water molecules.
PVC Short for polyvinylchloride, a type of plastic used in many building and plumbing applications.