In the compact "all-in-one" Blue Diversion Autarky (BDA) toilet, the researchers rely on two treatment steps for urine: Stabilisation with calcium hydroxide is followed by energy-efficient evaporation of the excess water, powered by ambient air. The hurdle to the small, technically not too complex and at the same time as robust as possible bathroom scale has thus at least been overcome for the volume reduction step. And because the first step greatly increases the pH value in the urine, germs are also killed. At the same time, handwashing and rinsing water is treated in the BDA module to such an extent that it can be reused for these purposes.
Prototypes of BDA urine treatment have already undergone intensive testing, from the Eawag campus in Dübendorf, to a Tiny Home and an SAC hut, to a site in Durban, South Africa . In collaboration with the University of Applied Sciences Northwestern Switzerland FNHW and the PSI, research has also been carried out on an extension to include a module with hydrothermal oxidation. This would also allow the faeces to be treated on site - leaving only water, carbon dioxide and a minimal amount of ash from inorganic substances.