“Blue Diversion AUTARKY” is the continuation of Eawag's RTTC project "Blue Diversion". The project developed technologies and prototype reactors for the on-site treatment of source-separated urine, feces and polluted water from anal cleansing and handwashing.

Urine treatment: (more details on the treatment processes is provided in the external links below)
Two processes are used in our system to treat the source-separated urine in the toilet: urine stabilization and water removal. Urine stabilization with calcium hydroxide prevents the formation of ammonia from urine (and thus the smell) and kills the pathogens. However, the high water content of urine – no matter if stabilized or not – requires significant storage capacity and can make the collection and transport to the agricultural fields very costly. Volume reduction through forced convection does not only reduce costs for storage and transport, but could also facilitate field application of the concentrated fertilizer.
We field-tested the urine treatment module in two applications: as part of a toilet system in South Africa and in a tiny-house application in Switzerland.

Water treatment:
The water treatment system, referred to as Water Wall, recycles hand washing water, toilet flush water (separated from the major part of urine and feces), or both. A multi-barrier approach with four treatment stages (bioreactor, ultrafiltration membrane, activated carbon filter and electrolysis) ensures that the water is safe for reuse. Water treatment prototypes were extensively tested under laboratory-conditions, under which they reliably removed pathogens, nutrients, malodor, and color from recycled water. However, when moving outside the laboratory, we expect a much higher variability of the number of users, composition of the water and external conditions. This is why we exposed different configurations of the Water Wall to real-life conditions.
We field-tested the Water Wall in three applications: as part of a toilet system and as part of a hand washing station in South Africa, and as part of a hand washing station in Switzerland.

Feces treatment:
The process used to treat the feces is called “hydrothermal oxidation” or HTO. When mixed with air and heated above around 400°C under high pressure, the fecal sludge decomposes and is oxidized completely to carbon dioxide and water. Ideally, the process is autothermal, meaning that the oxidation of the feces releases enough heat to maintain the high temperature. In the current project phase, we have been developing a comprehensive computer model of the reactor to improve understanding of the HTO process. We also improved the third prototype generation of the so-called FOX reactor (short for feces oxidation) and tested it with real users at Eawag (picture below).

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Product design and engineeringGlobalToilets or urinals (user interface)Treatment of wastewater or greywaterResource recovery Fundamental research and engineeringOtherBill & Melinda Gates FoundationFaeces or faecal sludgeGreywater or wastewaterUrineUniversity, education or research institution

Related Countries

Switzerland