In the region of West Bengal and Bangladesh there's a problem with the water. But, as Rose Hoban reports, an engineer from Northern Ireland thinks he has a way to solve it.

Much of the rock lining the underground aquifers in West Bengal and Bangladesh contains arsenic. For millennia, the element was in a form that didn't pose a danger to humans.

But over the past three or four decades, the Green Revolution occurred. Now, farmers apply tons of nitrogen-based fertilizers to their crops every year. These chemicals leach into underground aquifers. Over time, they've caused a reaction in the arsenic below ground, converting it to a form that dissolves easily in water.

Engineer Bashkar Sen Gupta from Queens University in Belfast, Northern Ireland, says as a result, an extraordinary number of people in West Bengal and Bangladesh now have arsenic poisoning. That number can be as high as one in every 100 people who are literally dying from drinking the water. 

"On an average," he adds, "five in 100 display other kinds of symptoms which is cancer-like and in the various stages of treatment and diagnosis."

Most efforts to treat the water have focused on filters to remove the arsenic. But they're slow… and they don't have a large enough capacity to adequately clean the amount of water needed for crop irrigation.

But now, Sen Gupta has come up with a low-tech solution to the arsenic problem that's based at the village level. It involves pumping water to the surface, aerating it to get more oxygen into it and returning it to the aquifer below. And the method is ingeniously simple.

"We are using showerheads," he explains. "The showerheads spray the water, it aerates and part of it will return using a thinner pipe back into the same aquifer zone."

Most local wells use energy to draw water from underground aquifers. That energy can be from a generator, or from a hand pump. But returning the newly aerated water to underground aquifers requires only a pipe and gravity.

"The equipment here is basically very simple," says Gupta. "You just need one pipe and few simple shower heads… plastic shower heads." The entire set-up costs the equivalent of US $100.

In the test systems Sen Gupta used, he found that one of these pumping systems could reduce the arsenic from an area of up to 90 meters in diameter around the pump site. He says it can treat enough water in a day to serve up to several hundred families. And the reduction in arsenic is dramatic.

"The first plant that we set up – which is 25 kilometers north of Calcutta – the first arsenic concentration that we recorded was 370 parts per billion, which is 37 times higher than the WHO limit," Gupta reports. "It took us about four weeks to bring it down to 20 parts per billion, and six weeks to bring it down to about two or three… parts per billion."

Sen Gupta is now working with Indian and Bangladeshi authorities to replicate his water treatment scheme. He's hoping to bring more of them online in the next several years.