An environmentally friendly and cost-effective method of sterilising water using CO2

Technology developed by UNSW Canberra researchers could provide an environmentally friendly, cost-effective method of sterilising water.

On 22 March, World Water Day, the United Nations will shine a light on the availability of clean water. Today, 2.1 billion people live without safe water at home and one in four primary schools have no drinking water service.

Developed by UNSW Canberra researchers, Dr Adrian Garrido Sanchis, Professor Richard Pashley and Australian National University Emeritus Professor Barry Ninham, the technology bubbles un-pressurised carbon dioxide (CO₂) through wastewater in a bubble column, effectively inactivating both bacteria and viruses.

This new technology is capable of sterilising water with hot CO2, which considerably reduces the energy requirements when compared with boiling water, as heating gas is much more efficient than heating water.

It is also safer than chemical treatments, such as chlorine.

Dr Sanchis first tried to inactivate viruses with a bubble column while he was completing his PhD at UNSW Canberra.

“The collision between the hot air bubbles and the viruses was the mechanism behind the inactivation,” he said.

“Then I tried to improve the inactivation effect with different solutions, with air at different temperatures and finally with different hot gases. This proved that hot carbon dioxide inactivated virus and bacteria faster than the other gases. Therefore, we decided to conduct a specific CO₂ pathogen inactivation study.”

Dr Sanchis said current water disinfection technologies have several limitations.

“This new technology could become a new sterilisation technology candidate able to compete with the existing ones,” he said. “The fact that the process can use heated CO₂ gas instead of heated water and the possibility of reusing exhaust gas from combustion processes makes the new process potentially more energy efficient.”

Australian Pork Limited (APL) has previously funded research into this new technology and is interested in supporting the next phase of the research towards commercialisation.

“APL funded the construction of a small pilot plant for pure water production from the condensation of the saturated gases from the bubble column,” Dr Sanchis said.

“This pilot plant was able to produce pure condensed water and also sterilise the piggery effluent, producing another output of sterilised water.

“Many waste disposal industries, like landfills, piggeries, waste-water treatment plants, bio-gas plants and coal power plants emit large amounts of CO₂. There is the potential for them to use these emissions in water treatment processes to sterilise water.”

The United Nation’s 2030 Agenda for Sustainable Development includes a target to ensure available and sustainable management of water for all by 2030. New technology, including this water sterilisation method, could contribute to achieving that goal.

Learn more: UNSW Canberra researchers develop new water sterilisation method