Due to the World Health Organization (WHO), 4 percent of all deaths are caused by poor drinking-water access, unimproved sanitation, and poor hygiene practices. Around 80 percent of people in urban agglomerations have access to drinking water from the tap. 96 percent receive drinking water from improved sources.
However, especially urban residents in developing countries struggle with diseases as a result of insufficient access to safe drinking water or improved sanitation. More than 500,000 diarrhoeal deaths are caused by contaminated drinking-water each year – estimated by WHO. The poor bacteriological quality of water can also cause cholera, dysentery or polio. Furthermore, viruses in water are still a challenge and limit the use of recycled water.
Water Sterilization With Un-pressurized Carbon Dioxide
Having said the above, we’re coming now to the positive developments – the efficient inactivation of viruses and bacteria. A research team at the University of New South Wales (UNSW) has tested an uncommon way of sterilizing water which could be more environmentally friendly as well as more cost-effective. Briefly: They found out that un-pressurized and heated bubbles – consisting of carbon dioxide – are able to inactivate viruses and bacteria effectively. As it is more efficient to heat gas than water, less energy is needed to exhaust the heated gas through the water than boiling it.
The specific thermal capacity of carbon dioxide with a temperature of 50°C is 0.864 kJ/(kg K). For the same temperature, water has a specific thermal capacity of 4.181 kJ/(kg K) which is more than 4,8 times higher than carbon dioxide. This is the reason why heating water needs many times more energy than heating carbon dioxide.
“The collision between the hot air bubbles and the viruses was the mechanism behind the inactivation. 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,” said Dr. Adrian Garrido Sanchis, researcher at the UNSW Canberra.