University of Florida Researchers Develop Filter Coating That Traps Bacteria and Viruses

August 05, 1998

GAINESVILLE, Fla. -- When 26 children became ill after swimming in a kiddie pool at an Atlanta water park earlier this summer, health investigators said it was because low chlorine levels failed to kill harmful bacteria in the water.

A coating developed by University of Florida engineers and biologists might have prevented the June accident by enabling the pool's filter to trap the E. coli bacteria -- one of many possible applications for the coating, the researchers say.

"The problem is, the filters in pools remove only a small fraction of the bacteria in the water, so they're really dependent on the chlorine for decontamination," said Ben Koopman, a professor in UF's department of environmental engineering sciences. "By using a filter that is enhanced in some way, you gain an additional barrier."

Koopman and three professors in chemical engineering, materials science and engineering and microbiology and cell science developed the coating as part of more than a decade of research in UF's Engineering Research Center (ERC). The Kimberly-Clark Corp. paid for some of the at-least $300,000 devoted to the research, with the ERC also contributing.

Dinesh Shah, professor of chemical engineering and director of the Center for Surface Science and Engineering, said the coating enables pool filters and other types of filters to trap bacteria, viruses and particles as small as 500 angstroms. One angstrom measures one ten-billionth of a meter. Viruses range in size from 500 to 1,000 angstroms, while the smallest bacteria measure about 10,000 angstroms, he said.

The key to the coating's effectiveness is its ability to give the filter a positive electrical charge, Shah said. Viruses, bacteria and tiny particles tend to be negatively charged, so the coating attracts the objects to the filter. The result is decontaminated water without the addition of chlorine or other chemicals, Shah said.

Tests of a coated swimming pool filter with contaminated water in a laboratory showed it trapped more than 90 percent of pathogens, compared with between 10 and 30 percent for the same uncoated filter, said Samuel Farrah, a professor of microbiology and cell science in UF's College of Agriculture.

But swimming pool filters aren't the only application, Shah said. Coated filters could also prove useful for soldiers or hikers whose only source of drinking water may be contaminated ponds or streams. While such water can be treated now with chlorine, the chemical does not eliminate toxins present in dead bacteria, and some bacteria are chlorine-resistant, Shah said.

"The idea is, you could supply a plastic bottle with this filter built-in," he said.

The coating may also prove useful to the silicon chip manufacturing industry, Shah said. Chip makers use large amounts of ultra pure water to polish silicon wafers. Depending on the availability and cost of water, they sometimes have to install purification or distillation equipment to recycle the water. These processes are expensive, and the filter coating promises a cheaper recycling technology, Shah said.

Shah, Koopman, Farrah and Brij Moudgil, professor of materials science engineering and director of the ERC, developed the coating. Several companies have expressed interest in developing the technology further for commercial purposes, Koopman said.

Writer: Aaron Hoover

Sources: Dinesh Shah, 352-392-0877; Ben Koopman, 392-7104
-end-


University of Florida

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