How to get drinking water clean without chlorine?

This morning I received the following interesting message :

Science Daily — University of Delaware researchers have developed an inexpensive, nonchlorine-based technology that can remove harmful microorganisms, including viruses, from drinking water.


Pei Chiu, an associate professor in UD’s Department of Civil and Environmental Engineering (UD = University of Delaware, USA), and Yan Jin, a professor of environmental soil physics in UD’s plant and soil sciences department, have developed an inexpensive, nonchlorine-based technology that can remove harmful microorganisms from drinking water, including viruses. UD’s patented technology, developed jointly by researchers in the College of Agriculture and Natural Resources and the College of Engineering, incorporates highly reactive iron in the filtering process to deliver a chemical “knock-out punch” to a host of notorious pathogens, from E. coli to rotavirus. The new technology could dramatically improve the safety of drinking water around the globe, particularly in developing countries. According to the World Health Organization (WHO), over a billion people–one-sixth of the world’s population–lack access to safe water supplies. Four billion cases of diarrheal disease occur worldwide every year, resulting in 1.8 million deaths, primarily infants and children in developing countries. Eighty-eight percent of this disease is attributed to unsafe water supplies, inadequate sanitation and hygiene.

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“What is unique about our technology is its ability to remove viruses–the smallest of the pathogens–from water supplies,” Pei Chiu said. Chiu and Jin sought the expertise of virologist Kali Kniel, an assistant professor in the animal and food sciences department, who has provided critical assistance with the testing phase.

“A serious challenge facing the water treatment industry is how to simultaneously control microbial pathogens, disinfectants such as chlorine, and toxic disinfection byproducts in our drinking water, and at an acceptable cost,” Chiu noted. Viruses are difficult to eliminate in drinking water using current methods because they are far smaller than bacteria, highly mobile, and resistant to chlorination, which is the dominant disinfection method used in the United States, according to the researchers.

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“By using elemental iron in the filtration process, we were able to remove viral agents from drinking water at very high efficiencies ………” Chiu noted.

The elemental or “zero-valent” iron (Fe) used in the technology is widely available as a byproduct of iron and steel production, and it is inexpensive, currently costing less than 40 cents a pound (~$750/ton). Viruses are either chemically inactivated by or irreversibly adsorbed to the iron, according to the scientists. Technology removes 99.999 percent of viruses.

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With partial support from the U.S. Department of Agriculture and the Delaware Water Resources Center, through its graduate fellowship program, the scientists and their students began evaluating the effectiveness of iron granules in removing viruses from water under continuous flow conditions and over extended periods. Two bacteriophages–viruses that infect bacteria–were used in the initial lab studies. Since then, Kniel has been documenting the technology’s effectiveness against human pathogens including E. coli 0157:H7, hepatitis A, norovirus and rotavirus. Rotavirus is the number-one cause of diarrhea in children, according to Kniel.

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The elemental iron also removed organic material, such as humic acid, that naturally occurs in groundwater and other sources of drinking water. During the disinfection process, this natural organic material can react with chlorine to produce a variety of toxic chemicals called disinfection byproducts.

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Applications in agriculture and food safety

Besides helping to safeguard drinking water, the UD technology may have applications in agriculture. Integrated into the wash-water system at a produce-packing house, it could help clean and safeguard fresh and “ready to eat” vegetables, particularly leafy greens like lettuce and spinach, as well as fruit, according to Kniel. “Sometimes on farms, wash-water is recirculated, so this technology could help prevent plant pathogens from spreading to other plants,” she said.

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This seems to be a very promising technology indeed ! Developing countries will be highly interested.

Author: Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.

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