Shedding new light on how to disinfect water

Researchers in Athlone and Galway are shining a bit of light on contaminated water supplies in the hope of ending the need for "boil water" notices.

They use a light source that can clear out all bacterial contamination and can even knock out the dreaded Cryptosporidium organism which is a danger to human health.

Admittedly this is light of a different kind.

It is an intensely bright white light that has been "enriched" with a little added ultra violet (UV) to boost its antibacterial activity, explains Prof Neil Rowan of Athlone Institute of Technology and the lead investigator of the project.

It is delivered as a bright flash "similar to a lightening flash", he says. Its effectiveness comes from being "high pressure" light delivered in rapid-fire pulses from 10 up to 100 pulses per second. "Pulsed light constitutes a next generation approach to ultraviolet light disinfection, " says Rowan.

The use of UV light to disinfect water supplies probably sounds very familiar given that it has been around for decades. It even features from time-to-time in student projects presented at the BT Young Scientist and Technology Exhibition at the RDS.

It is used in a very low-tech, but effective, way in Africa where Irish researchers have helped communities there fine-tune the simplest UV sterilisation approach, using sunlight.

Large plastic bottles are filled with contaminated water and then set in the sun where heat and UV conspire to kill off many bacterial forms such as E coli.

UV light is used in waste water treatment and air purification and many water treatment plants use UV light to kill off antibiotic-resistant bacteria.

But these systems can't deal with the Cryptosporidium parvum parasite, says Rowan. It survives chlorination and lurks in many public water supplies, ready to cause human illness.

The Environmental Protection Agency (EPA) lists 36 water schemes as being "inadequate" in treating Cryptosporidium, supplies which currently serve almost 210,000 people. Ireland has one of the worst records in the EU for this contaminant.

Enter Rowan who heads biosciences research at Athlone, Dr Mary Garvey the lead postdoctoral research fellow and Dr Eoghan Clifford from NUI Galway and colleagues, who with funding from the EPA began developing a pulsed light disinfection system capable of tackling Cryptosporidium.

Along the way they delivered six peer-reviewed research papers for novel treatment and assessment methods and the technology itself. “Many labs don’t want to work with Cryptosporidium,” Rowan says. “You need special facilities in the lab and we had to develop new ways to assess how effectively our systems worked. We had to be able to confirm whether the organism, which is like a cyst or a spore, was infectious or noninfectious after treatment.”

Rowan, who is also adjunct professor of medicine at NUI Galway, started as a microbiologist but was also involved in developing novel technologies in an engineering context. He resorted to high voltage engineering to come up with a treatment method that delivers pulsed high intensity light that causes irreversible DNA damage to kill off ordinary bacteria and the parasites.

It is like driving a nail into a wall with a hammer. “It is like a nail, you need a lot of energy to get a nail into a wall and this is similar, going bang with a hammer but using packets of energy. It is a more efficient delivery system and a next generation approach to energy delivery.”

The light packets used to knock out the bugs are created with 1,000 volts of electricity released through a specialised light source. High pulse rates are possible but the system works happily at 10 pulses per second.

This will be a bolt-on technology used at the treatment plant to provide additional support to existing treatment facilities, he believes.

They proved their system will work in the context of a large water treatment facility and are epitomising the system to turn it into a commercial opportunity. “We are looking at routes to market. This is bringing UV light into its fourth generation,” he says.

It is also a green technology, he argues. “It doesn’t leave any lingering chemicals, there are no by products left behind. It is an illumination process so it is clean, it is a green technology.”

He says that this will not end the battle against Cryptosporidium and new approaches have to be developed all the time. “In terms of microbial evolution you have to look at new ideas. Microbes have an immense ability to adapt, for example the way they can adapt to chlorine. But they won’t be able to adapt to this [system],” he says.

Finding solutions to threats to drinking water was an imperative, says EPA deputy director general Dara Lynott. It addresses a drinking water quality challenge but also provides “green economic opportunities” for Ireland.