Ashok Gadgil, LBNL

Contact: Ashok Gadgil, 510-486-4651, ajgadgil@lbl.gov

Role in the Energy-Water Nexus

Scientists at Lawrence Berkeley National Laboratory (LBNL) have invented a process for cost-effectively removing high concentrations of arsenic from drinking water. Arsenic in drinking water is a serious problem in various regions, including Bangladesh and neighboring parts of India and Nepal. The World Health Organization estimates that in Bangladesh alone the problem affects almost 60 million people, rendering it the largest case of mass poisoning in human history. Arsenic removal typically requires significant energy input; the LBNL process requires significantly less energy input.

Research Objectives

LBNL has developed a method (patent pending) to remove arsenic from drinking water to a level that meets the proposed U.S. Environmental Protection Agency (EPA) limit of 10 parts per billion (ppb), which will go into effect in January 2006. Because the material used to remove the arsenic is a waste product, treatment costs are far lower than for current technologies. Based on EPA estimates, the best current technology that achieves comparable arsenic removal for small water systems costs between $58 and at least $327 per household per year. Based on initial laboratory tests, the cost for all the materials in our arsenic removal medium is less than $1 per household per year, assuming 2.2 persons per household, 1,000 liters of water per day per person, an inlet arsenic concentration of 50 ppb (the current EPA limit), and a treated water concentration of 10 ppb (the new EPA limit). This estimate does not include reactor costs, which should be one-time only and which we hope to address in the next phase of our research.

Approach

LBNL is using bottom ash (a finely powdered, sterile waste material from coal-fired power plants) as the primary ingredient in the arsenic-removal process. After particles of bottom ash are coated with ferric hydroxide in a simple five-step process, the “LBNL medium” reacts with, removes, and immobilizes arsenic in water, achieving levels previously unattainable without costly materials and equipment.

Accomplishments

We have made several batches of “LBNL medium” that have lowered arsenic concentrations in various waters, including laboratory water spiked to 2.4 parts per million (ppm) arsenic, water obtained in India at arsenic concentrations ranging from just under 70 to more than 150 ppb, and water obtained in Sonoma, California, that had an arsenic concentration of approximately 60 ppb. In all cases, the LBNL medium produced water containing arsenic concentrations less than 10 ppb.

Significance of Findings

Our laboratory results indicate that 5 grams of our medium can reduce arsenic concentrations in 2.4 liters of water from 2,400 to 10 ppb. Assuming linearity, this result is equivalent to needing just 4 grams of medium to reduce arsenic concentrations from 50 to 10 ppb in 100 liters of water. Treating 100,000 liters of water from 50 down to 10 ppb arsenic (equivalent to a small municipal system) is expected to require about 4 kilograms of the medium, for which total materials costs are estimated to be less than $0.10.

Publications

Gadgil, A.J., 2004: A method to remove arsenic species from an aqueous medium, U.S. Patent Application by Lawrence Berkeley National Laboratory.

Acknowledgements

This work was supported by the California Energy Commission, the Blue Planet Run Foundation, and an exploratory grant from the Technology Transfer Department at LBNL. The work was performed under U.S. Department of Energy Contract DE-AC03-76SF0098.