New Technology Removes Harmful Microorganisms from Drinking Water
University of Delaware (UD) researchers announced on Feb. 26 the development of an inexpensive, nonchlorine-based technology that can remove harmful microorganisms, including viruses, from drinking water.
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, researchers said. According to the World Health Organization (WHO), more than one billion people (about 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.
In the United States, viruses are the target pathogenic microorganisms in the new Ground Water Rule under EPA's Safe Drinking Water Act.
"What is unique about our technology is its ability to remove viruses -- the smallest of the pathogens -- from water supplies," said Pei Chiu, an associate professor in UD's Department of Civil and Environmental Engineering.
Chiu collaborated with Yan Jin, a professor of environmental soil physics in UD's plant and soil sciences department, to develop the technology. They then 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.
"By using elemental iron in the filtration process, we were able to remove viral agents from drinking water at very high efficiencies. Of a quarter of a million particles going in, only a few were going out," Chiu noted.
According to the researchers, 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. Viruses are either chemically inactivated by or irreversibly adsorbed to the iron, according to the scientists.
The idea for the UD research sprang up when Jin and Chiu were discussing their respective projects over lunch one day.
Since joining UD in 1995, Jin's has primarily investigated the survival, attachment and transport behavior of viruses in soil and groundwater aquifers. One of the projects, which was sponsored by the American Water Works Association Research Foundation, involved testing virus transport potential in soils collected from different regions across the United States. Jin's group found that the soils high in iron and aluminum oxides removed viruses much more efficiently than those that didn't contain metal oxides.
"We knew that iron had been used to treat a variety of pollutants in groundwater, but no one had tested iron against biological agents," Chiu said. So the two researchers decided to pursue some experiments.
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 No. 1 cause of diarrhea in children, according to Kniel.
"In 20 minutes, we found 99.99 percent removal of the viruses," Chiu said. "And we found that removal of the viruses got even better than that with time, to more than 99.999 percent."
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.
"Our iron-based technology can help ensure drinking water safety by reducing microbial pathogens and disinfection byproducts simultaneously," Chiu noted.
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.
Pei Chiu: http://www.ce.udel.edu/~pei