HKUST scientists invent new water purifier

Tiny device may clean your water without cleaning out your bank account

PUBLISHED : Thursday, 17 July, 2014, 4:23am
UPDATED : Thursday, 17 July, 2014, 4:23am

A research team at the University of Science and Technology has invented a low-voltage pulsed electric field device that can kill more than 99 per cent of waterborne bacteria in seconds.

The device, which costs HK$10 to HK$20 per unit to produce and can run on two AA batteries for up to six months, is being tested at Queen Elizabeth Hospital in Yau Ma Tei.

If all goes well, it could replace hospitals' costly HK$5,000 medical-grade filters that have to be changed every few weeks - and even make it into homes.

"The major motivation behind this is that we typically find water from treatment plants very clean. But once it goes into piping for distribution, it usually gets contaminated," said Professor Yeung King-lun, of the chemical and biomolecular engineering department.

Yeung led the team in the HK$1 million government-funded research alongside Professor Joseph Kwan Kai-cho, director of the university's health, safety and environment office.

"Water from your home is safe, but it's not 100 per cent free of micro-organisms. We wanted to find a way to better disinfect water, given that we have issues with Legionella in Hong Kong from time to time," Yeung said.

The waterborne Legionella pneumophila bacteria is responsible for most cases of legionnaires' disease, a form of pneumonia. Other common waterborne pathogens include E coli, aeromonas and mycobacterium.

The World Health Organisation estimates that more than two billion cases of illness each year are caused by the consumption of unclean water.

Existing water disinfection technologies such as chlorination produce pungent smells and toxic by-products, while heating and reverse osmosis consume energy and are costly.

"The idea is to find a technique that disinfects water without changing the water quality," Yeung said, adding that the team's vision of creating a device usable both in hospitals and at home required them to miniaturise the technology, increase the electrodes' efficiency and redesign the electrode material.

"The device uses a pulse electric field that pulses at 100 times a second. The ultimate effect is that the pores of the bacteria's cell walls become enlarged, resulting in the materials and cytoplasm within the cell flowing out through the holes. As such, the bacteria dies," Kwan said.

Kwan was recently named a Distinguished Fellow by the American Industrial Hygiene Association for his contributions in the field of industrial safety, hygiene and infection control.

"The aim is to have the device developed as a household product," he said.