Hot CO2 technology efficiently sterilises water

Technology developed by UNSW Canberra could provide an environmentally friendly, cost-effective method of sterilising water. Developed by UNSW Canberra researchers Dr Adrian Garrido Sanchis, Professor Richard Pashley and Australian National University Emeritus Professor Barry Ninham, the technique bubbles unpressurised carbon dioxide (CO₂) through wastewater in a bubble column, effectively inactivating bacteria and viruses.

The technology is capable of sterilising water with hot CO₂, which considerably reduces the energy requirements compared with boiling water, as heating gas is much more efficient than heating water. The method is also safer than chemical treatments such as chlorine.

Dr Sanchis first tried to inactivate viruses with a bubble column while 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[es] and bacteria faster than the other gases. Therefore, we decided to conduct a specific CO₂ pathogen inactivation study.”

Dr Sanchis explained that 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 re-using exhaust gas from combustion processes, makes the new process potentially more energy efficient.”

Australian Pork Limited (APL) has previously funded research into the 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, wastewater treatment plants, biogas 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.”

On 22 March, World Water Day, the United Nations shone a light on clean water availability. Today 2.1 billion people live without safe water at home and one in four primary schools has no drinking water service. The United Nations’ 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 help achieve that goal.

Image credit: ©stock.adobe.com/au/Zaichenko Olga