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For Millions of Bangladeshis, Ash May Offer Hope

Innovative filter could also help California comply with tighter U.S. EPA arsenic drinking-water standard.

Ashok Gadgil, a scientist in the Environmental Energy Technologies Division at Lawrence Berkeley National Laboratory (Berkeley Lab), is developing a cheap and effective way to provide safe drinking water to 60 million Bangladeshis who live with the threat of arsenic poisoning. Gadgil's idea is to create arsenic filters from coal ash, the fine gray powder that piles up, waiting to be discarded, at the bottom of furnaces at all coal-fired power stations.

"It's just coal ash, nothing fancy," says Gadgil. "But it could save so many lives."

Ash particles before coating with ferric oxide Ash particles after coating with ferric oxide

Figure 1. Bottom ash before (left) and after coating with ferric oxide

Arsenic poisoning in Bangladesh has been called one of the largest mass poisonings in human history, expected to cause 10 percent of all future adult deaths in the impoverished nation of 130 million. For reasons not entirely understood, the shallow tube-wells that Bangladeshis depend on for water contain dangerous concentrations of the toxic substance; if ingested at these concentrations over long periods of time, arsenic leads to debilitating lesions, cancer, and death.

Although still in the investigational stage, Gadgil's technique would involve coating the ash with a compound that attracts arsenic, filling tea bag-sized pouches with the powder, and distributing the filters throughout the countryside, one per family per day. Water drawn from any one of the millions of contaminated wells that dot Bangladesh could then be poured through the filter and safely consumed.

It's difficult to believe that one person, armed only with a handful of ash and a few promising lab tests, might derail a catastrophe looming on the other side of the globe, but Gadgil has an uncommon drive to find affordable ways of providing safe drinking water to thousands of people. In November 2004, he received an award from California's Tech Museum of Innovation in San Jose, which honors people who use technology to help humanity, for developing a water-purification system that kills bacteria with ultraviolet (UV) light. The system, called UV Waterworks and marketed by WaterHealth International, Inc., is used daily by about 300,000 people in Mexico, the Philippines, and several other countries, and several systems will soon be installed in Gadgil's native India. Now, Bangladesh weighs heavily on his mind.

"The magnitude of the problem is overwhelming. We have to develop a solution that is affordable and effective," says Gadgil.

After receiving $5,000 in seed funding from the Berkeley Lab Technology Transfer Department in 2003, Gadgil set out to develop a filter that meets these criteria. His options quickly narrowed: he needed a material that has a high surface-to-volume ratio, is pathogen free, and is available in large quantities at low cost. Reflecting on carbon as a commonly used filtration medium, Gadgil thought about leftover coal ash, the large piles that collect at all coal-fired power stations, waiting to be sent to landfills. An additional $20,000 in seed funding from the Blue Planet Run Foundation helped him explore this option.

Christina Galitsky filters water after it has been mixed with the arsenic removal medium

Figure 2. Researcher Christina Galitsky filters water after it has been mixed with the arsenic removal medium.

Coal ash is composed of particles that measure between one and 10 microns in diameter, much smaller than a 100-micron-diameter human hair. This means that even a small volume of the powder has a lot of surface area, maximizing the opportunity for surface reactions to snare arsenic. The ash is also heated to 800 degrees Celsius during the coal burning process, so it's sterile and free of volatile compounds. And it's plentiful. Coal-fired power plants provide most of neighboring India's electricity, and the locally mined coal used is uniquely suited for Gadgil's purposes: it's only 60 percent carbon, meaning 40 percent becomes ash.

After obtaining some ash from India, he assembled Team Arsenic, which includes Lara Gundel, Yanbo Pang, Christie Galitsky, Duo Wang, and Anna Blumstein. Together, they developed a way to coat each ash particle with ferric hydroxide, a chemical that reacts with arsenic and forces the element to precipitate onto the particle (see Figure 1). Initial tests indicate this specially treated coal ash makes a very powerful filter. After spiking lab water with so much arsenic that its concentration soared to an extremely toxic 2,400 parts per billion (ppb), the team found that the filter lowered the water's arsenic concentration to 10 ppb (see Figure 2). The Bangladeshi standard for safe drinking water is 50 ppb.

Gadgil estimates that five grams of filter material could render about three gallons of Bangladeshi well water—with an average arsenic concentration of 400 ppb—safe to drink. Put another way, a filter the size of a tea bag could provide drinking water for a family of six for one day. He also estimates the technique will cost about thirty cents per person per year. The next-best option is a filter developed by a Bangladeshi engineer, backed by the non-profit organization IDE-International, that uses pulverized brick instead of ash. It would cost $9.70 per person per year.

Closer to home, the California Energy Commission's Public Interest Energy Research program recently awarded Gadgil $250,000 to explore whether a variation of this technique can help the state comply with a U.S. Environmental Protection Agency rule, effective in 2006, that tightens the U.S. arsenic drinking water standard from 50 ppb to 10 ppb. Currently, 600,000 California residents consume water with concentrations above 10 ppb. Gadgil will determine whether ash derived from U.S. coal can be developed into a filtration system and whether such a system can work at small municipal water treatment facilities.

Initial results appear promising. Currently, the cost of arsenic removal at small municipal water systems ranges from $58 to $327 per household per year. Gadgil estimates that his method would cost less than $1 per household per year, not including the one-time cost of coating the ash with ferric hydroxide.

In addition to this research close to home, Gadgil will also intensify his efforts to help Bangladesh—if he secures more funding. His filter requires many more tests and refinements, but he knows the payoff could be huge.

"If this succeeds, it will be a life-saving and affordable technology for tens of millions of people," he says.

— Dan Krotz

For more information, contact:

  • Dan Krotz
  • (510) 486-4019; Fax (510) 486-6641

Dan Krotz is a writer in Berkeley Lab's Public Information Office.

This research is funded by the Lawrence Berkeley National Laboratory's Technology Transfer Department and the Blue Planet Run Foundation, and the California Energy Commission's Public Interest Energy Research Foundation.

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