Abertay team devises chemical-free disinfectant system

One famous disinfectant’s claim to kill 99.9% of germs stone-dead has entered advertising folklore, but a team from the University of Abertay Dundee has gone literally a thousand times better.

Abertay researchers have devised a method of killing bacteria in water using microbubbles and ozone that has succeeded in destroying 99.9999% of E.coli bacteria in a given volume of water.

Ozone is increasingly used as an alternative to chlorination in the modern food and drink industry, but normally only eliminates 99.99% of bacteria. The Abertay team’s results from combining ozone with microbubbles are generating considerable interest among manufacturers seeking a means of ensuring ultrapure and almost completely bacteria-free water for use in food processing, without using potentially harmful chemicals.

Rashmi Chand, a PhD student in Abertay’s School of Contemporary Sciences, employed hydrodynamic cavitation technology which pumps water very fast along a pipe and then through a small hole with such force that microbubbles or cavities are produced. These bubbles then implode, creating tiny pockets of high pressure and high temperature that kill bacteria.

The hydrodynamic cavitation by itself killed off 99 million out of 100 million E.coli cells in a body of water. Working with Abertay’s Professor David Bremner, Rashmi then investigated the effect of adding ozone and discovered that two bursts of the gas during the process further reduced the E.coli count to fewer than 100 cells.

Rashmi explained: “Food is a necessary for life, and safe food is essential for human health. In processing the food, ultrapure and completely bacterial free water is of prime importance.

“Conventional chemical disinfection techniques, particularly chlorination, suffer from disadvantages such as the formation of possibly carcinogenic by-products. Our method of disinfection by means of ozone and hydrodynamic cavitation opens up the possibility of eliminating or drastically reducing the use of these disinfecting chemicals,” she added.

The project was supported by the Food Processing Faraday Partnership Ltd (FPFP), which aims to promote improved interactions between the UK science, engineering and technology base and the UK food manufacturing industry.

FPFP were interested in the specialized ultrasound and hydrodynamic equipment available only at Abertay and provided a small grant to fund the acquisition of an ozoniser and enable the six-month research project to go ahead.

The Abertay team’s results are due to be published in a scientific journal in the near future.

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