In a rural, remote village in the southeastern part of Bangladesh, an aid worker
stands in the yard of a villager who wants to install a well for drinking water.
The worker pulls out a cell phone and calls up statistical data that indicates
how deep to drill the well to reach clean water. Workers then manually drill
an exploratory well to that depth and send a sampling needle deep
into the ground. Like drawing blood from a vein, the needle pricks
the aquifer and draws up a vial of water, which the aid worker then tests for
contaminants, such as arsenic, at the surface. If the water proves safe, people
can install a well there. If not, they drill deeper and retest, until they reach
safe water. All told, the testing process, which should provide a clean source
of water for drinking and cooking for the villagers family, adds about
an hour to the well-installation process.
Although this particular scene has happened only in a pilot test, the technology is already available and it hopefully will be deployed more widely soon, says Alexander van Geen, a geochemist at Columbia Universitys Lamont-Doherty Earth Observatory in Palisades, N.Y. The needle sampler and cell-phone system are only one idea for finding safe water in Bangladesh, where naturally occurring arsenic is a huge problem, he says, as well as in other South Asian developing countries such as Cambodia, Vietnam, China and West Bengal in India, where altogether at least 100 million people are exposed to arsenic in high doses, according to the World Health Organization (WHO).
Researchers recently developed the arsenic needle sampler the big needle and transparent tube that the man in the picture is holding to test the groundwater before a well is installed. They hope that figuring out where to install a well before drilling will help Bangladeshi villagers have a clean water source. Photo by Alexander van Geen.
WHO considers concentrations over 10 micrograms of arsenic per liter of water
to be too high. Bangladeshs standard is 50 micrograms per liter. At least
90 percent of the countrys population of 130 million people drink well
water, according to WHO, and there are at least 10 million wells in the country,
van Geen says. Studies by the British Geological Survey over the last decade
show that at least one-third of those wells have arsenic concentrations above
the Bangladesh standard, and more than half are above the WHO standard. Those
studies mean that at least 50 million people in Bangladesh alone are drinking
water with potentially dangerous arsenic levels.
Arsenic poisoning in Bangladesh is a problem of epidemic proportions, says Joseph Graziano, associate dean for research at the Mailman School of Public Health at Columbia University. It increases rates of skin, bladder, lung and liver cancer, as well as strokes, heart attacks, cardiovascular disease and skin lesions. And now were beginning to see lesions on children as young as 6 months old, and developmental and neurological effects similar to those associated with lead poisoning on children as young as 10, Graziano says (see story, page 22). Generally, it takes about a decade or more for cancers and heart problems to start showing up in people who have been exposed to arsenic.
In Bangladesh, people used to collect most drinking and cooking water from a plethora of surface sources such as ponds and streams. But in the 1970s, health officials determined that the surface water was contaminated with pathogens and was spreading diseases, including diarrhea, dysentery, typhoid, cholera and hepatitis. To solve the problem, they drilled wells and encouraged households to switch to groundwater, which was clear of disease. These community wells were so popular, van Geen says, that individual households followed suit by installing personal wells, thus doubling the number of wells in the country every five years. But in 1993, arsenic was discovered in the groundwater. By then, people had been exposed to varying levels of the poisonous metal for close to two decades, and some health officials worry that arsenic-based diseases may reach epidemic proportions in years to come.
Academia, the government of Bangladesh and international nongovernmental organizations have been studying the problem ever since, trying to figure out how widespread the problem is, as well as come up with a solution, van Geen says. They have considered a number of approaches, including installing household water filters, remediating surface water, collecting rainfall and building reservoirs to hold it, or removing arsenic from the groundwater.
But problems exist with each of these suggestions, says Charles Harvey, a hydrologist in the civil and environmental engineering department at MIT. Studies indicate that people may be reluctant to use water filters regularly, for example, and the filters also create waste sludge that has to be disposed of somewhere else, he says. The best option for at least the next decade or two, van Geen and colleagues say, is to get the people of Bangladesh to switch to cleaner wells.
The people of Bangladesh know that arsenic is a problem and will do what they can what is practical to solve the problem on an individual basis, van Geen says. And there is a lot of clean, safe groundwater in the country, he says; it just has to be found.
Research has shown that deeper aquifers at depths varying from 30 to more than 150 meters appear to be relatively safe. But part of the problem with simply switching everyone to deeper wells, Harvey says, is that very little is known about the subsurface. The technologies used in the developed world to study groundwater are not being employed there, he says, such as multilevel sampling of an aquifer and building detailed groundwater flow models.
Van Geen and colleagues have developed the cell-phone-based system to call up information onsite and in real time about any given well, and they already have a database of arsenic concentrations in groundwater in close to 300,000 wells in 300 villages in Bangladesh that were tested through a World Bank-sponsored program. They hope, van Geen says, to add arsenic concentration levels into the accessible database from an additional 5 million wells.
Automatically plugging in data from nearby wells from the database, the system utilizes a statistical algorithm developed by Columbia statistics professor Andrew Gelman to estimate the probability that a particular location will have low-arsenic water at a particular depth, as presented in a paper in the December 2004 Risk Analysis. Via cell phone, consultants then receive a text message with the automated calculation of how deep to drill to reach safe water.
Workers then drill to that depth and use the needle sampler, prototypes of which have been made from components that could be easily produced in Bangladesh, van Geen says, to draw up the water for final testing. The needle sampler is composed of a clear PVC sample chamber, an 18-inch needle and a unit to connect the needle to the sample chamber. The consultants then test the water using an arsenic field kit (that has been in use for years) to directly measure the arsenic concentration in the water before installing a well or digging to a deeper aquifer in an existing hole. The whole system is easy enough to use that the local drillers in individual communities could be trained to use it eventually, van Geen says. The researchers published the results of this pilot project in the December 2004 edition of Environmental Science & Technology.
Actually, the arsenic needle is a cheap and simple model of what is used in the United States to sample groundwater, says Harvey, who was not involved in the project. It is a tool, he says, to help us to learn more about the geochemistry of the water.
Still, some scientists remain convinced that the best solution is yet to be found. The U.S. National Academy of Engineering (NAE), for example, recently announced a competition (sponsored by the Grainger Foundation) to find a treatment option for the arsenic-laced water in Bangladesh and other affected developing countries. Jack Fritz, senior program officer at NAE, says that $1 million will go to the person or group who develops the best practical technology to treat the water. Although the winners are allowed to do whatever they want with the prize money, the hope is that they will put the money to use on implementing their technology in a developing country, Fritz says. Were trying to energize the American engineering community to help the developing world, he says.
Getting and keeping the developed world involved is important, Harvey says, but funds are tight. And, Graziano adds, while the developed world now accepts that arsenic poisoning is a huge problem, high impending cancer rates may not be a compelling enough reason to get them to act. Nonetheless, Graziano says, I hope that theres a more concerted effort in the next 10 years to curb this problem than there has been over the last 10 years.
"Leads Toxic Urban Legacy and Childrens Health," Geotimes, May 2005
U.S. National Academy of Engineering (NAE) competition (sponsored by the Grainger Foundation)
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