Blue Diversion AUTARKY – Abwasserbehandlung ohne Netzanschluss

AUTARKY im Überblick

In Autarky entwickeln wir kleine Anlagen für die getrennte Behandlung von Urin, Abwasser und Fäkalien direkt in der Toilette. Ziel ist es den Menschen ohne Zugang zu sanitärer Versorgung eine Toilette zur Verfügung stellen zu können, die keinen Anschluss an Wasser- und Abwasserleitungen benötigt, also autark ist. Durch die Trennung von Urin, Abwasser und Fäkalien an der Quelle, können die drei Ströme entsprechend ihrer besonderen Eigenschaften behandelt werden. Die Trennung erlaubt eine maximale Rückgewinnung von Nährstoffen und Frischwasser.


Das Autarky-Team entwickelt Anlagen für die Behandlung von Urin, Fäkalien und Wasser. Bei der Urinbehandlung wird dieser durch die Zugabe von Kalziumhydroxid zunächst stabilisiert und anschliessend verdunstet. Übrig bleibt ein Mix aus verschiedenen Salzen. Die Fäkalienbehandlung basiert auf dem Prinzip der superkritischen Wasseroxidation (SCWO) wobei die Endprodukte Kohlendioxyd, Wasser und ausgefällte anorganische Feststoffe entstehen. Bei der Wasserbehandlung sorgt ausschliesslich Gravitation dafür, dass schmutziges Wasser durch die Membrane gefiltert wird. Auf der sogenannten „Gravity Driven Membrane (GDM)“ gewährleistet ein Biofilm konstanten Wasserdurchfluss. Mit der Hilfe weiterer einfacher Behandlungsmethoden zur Beseitigung von Mikroorganismen kann das Wasser zum Händewaschen und Spülen benutzt werden.

Mehr zu Wasserbehandlung

The preceding project Blue Diversion, achieved tremendous progress towards developing gravity driven membrane technology (GDM) into a practical toilet water recycling system for urban developing world applications. The goal of AUTARKY is to better understand and verify the safety of our system with respect to the user and to explore alternative technologies which may reduce capital and energy costs. We are also examining how the same membrane technology functions in systems representing higher and lower organic and nutrient loading.

The gravity driven membrane of the Blue Diversion Toilet has a permeability of approximately 3-4 L/h respectively 1-1.5L/h/m2. It filtrates water for handwashing and flushing for about 50 uses per day (10 users).

The gravity driven membrane achieves approximately 95% removal of organic carbon entering the system. Additional treatment is required to maintain microbial stability within the clean water tank. Microbial stability refers here to water with limited potential for contamination and growth of pathogens. The electrolysis unit in the previous version of the toilet has demonstrated an ability to reduce organic carbon concentrations and produce a chlorine residual, both of which help to limit pathogen growth.

Treatment technologies such as activated carbon, ozone and UV light are being considered as alternatives to the electrolysis. These alternatives may be less expensive to install and maintain, and they may produce superior water quality given considerations such as their impact on biology of the membrane. The advantages and disadvantages of each technology will be first evaluated in batch; promising technologies will then be integrated into full-scale toilet systems. A quantitative microbial risk assessment will be performed on the entire module. In this regard, pathogen surrogates are used to investigate passage through the membrane and in competitive experiments with the natural bacteria community which forms in the clean water reservoir.

Further information on gravity driven membranes

Project: Gravity-Driven Membrane (GDM) technology


Derlon, N.; Mimoso, J.; Klein, T.; Koetzsch, S.; Morgenroth, E. (2014) Presence of biofilms on ultrafiltration membrane surfaces increases the quality of permeate produced during ultra-low pressure gravity-driven membrane filtration, Water Research, 60, 164-173, doi:10.1016/j.watres.2014.04.045, Institutional Repository
Ravndal, K. T.; Künzle, R.; Derlon, N.; Morgenroth, E. (2015) On-site treatment of used wash-water using biologically activated membrane bioreactors operated at different solids retention times, Journal of Water Sanitation and Hygiene for Development, 5(4), 544-552, doi:10.2166/washdev.2015.174, Institutional Repository
Chomiak, A.; Traber, J.; Morgenroth, E.; Derlon, N. (2015) Biofilm increases permeate quality by organic carbon degradation in low pressure ultrafiltration, Water Research, 85, 512-520, doi:10.1016/j.watres.2015.08.009, Institutional Repository

Mehr zu Urinbehandlung

Two processes are necessary to treat the source-separated urine in the toilet: urine stabilization and water removal. Stabilization is necessary to avoid malodour which occurs during storage, to inactivate pathogens and to conserve the valuable nutrient urea. Once the urine is stabilized the volume of the urine will be reduced by evaporation, the remaining end-product is a mix of salts. After further external treatment steps these salts can be used as fertilizer in agriculture.


Urine stabilization in detail

The main goal of this treatment step is to prevent urea hydrolysis, which is a process that converts urea to ammonia and carbon dioxide. Through the addition of calcium hydroxide to fresh urine the pH increases to values above 12 and prevents microbial urea hydrolysis. An additional benefit of the high pH value is the killing of pathogens and the prevention of biological processes that produce malodour.

When Ca(OH)2 is added to the urine  only about the amount dissolves, which is needed to reach the necessary high pH value. This allows providing a depot of Ca(OH)2 in the stabilization tank; therefore no expensive and complicated dosage mechanisms are required. Moreover, calcium hydroxide is a cheap reagent and readily available worldwide. An additional benefit of Ca(OH)2 dosage is the precipitation of calcium phosphate. This mineral could be recovered apart from the other urine compounds and used for fertilizer production.

Sedimentation of calcium phosphate in stabilised fresh urine
Sedimentation of calcium phosphate in stabilised fresh urine
Filtration of stabilised fresh urine
Filtration of stabilised fresh urine


Udert, K. M.; Larsen, T. A.; Biebow, M.; Gujer, W. (2003) Urea hydrolysis and precipitation dynamics in a urine-collecting system, Water Research, 37(11), 2571-2582, doi:10.1016/S0043-1354(03)00065-4, Institutional Repository
Randall, D. G.; Krähenbühl, M.; Köpping, I.; Larsen, T. A.; Udert, K. M. (2016) A novel approach for stabilizing fresh urine by calcium hydroxide addition, Water Research, 95, 361-369, doi:10.1016/j.watres.2016.03.007, Institutional Repository

Decrey, L., and Kohn, T. (2017) Virus inactivation in stored human urine, sludge and animal manure under typical conditions of storage or mesophilic anaerobic digestion,  Environmental Science: Water Research & Technology  

Urine water removal in detail

The direct application of human urine as fertilizer is a common practice in many rural areas worldwide. However, the high water content of urine – no matter if stabilized or not – requires significant storage capacity and can make the transport to the agricultural fields very costly. Volume reduction does not only reduce costs for storage and transport but could also facilitate field application of the concentrated fertilizer. Standard volume reduction techniques are most often energy intensive processes, because they require high temperatures (distillation) or pressures (reverse osmosis).


We are currently focusing on several evaporation techniques, which do not require any heating and pressurizing processes. One example is the evaporation pipe (see picture 2) where urine is trickled down a pipe, which is aerated with ambient air that takes up water. Our goal is to recover a hygienically safe end-product that concentrates valuable nutrients that will be applied to cropland.


Antonini, S., et al. (2012). "Solar thermal evaporation of human urine for nitrogen and phosphorus recovery in Vietnam." Sci Total Environ 414: 592-599.

Pahore, M. M., et al. (2010). "Rational design of an on-site volume reduction system for source-separated urine." Environ Technol 31(4): 399-408.

Evaporation of stabilized urine

First lab tests: Urine trickles down through the inner surface of the evaporation pipe while air is forced upwards causing urine to dry progressively.
First lab tests: Urine trickles down through the inner surface of the evaporation pipe while air is forced upwards causing urine to dry progressively.

Mehr zu Fäkalienbehandlung

In the Autarky toilet, feces are separated from urine and collected in a container at the bottom of the toilet. They may contain harmful compounds such as pathogens and must be inactivated quickly to avoid anaerobic decomposition and the emission of malodorous gases.


Frédéric Vogel (PSI/ FHNW)

In our approach the organic matter of the feces sludge is completely mineralized to carbon dioxide, water and minerals such as phosphate salts. The remaining streams are off-gas and a mixture of water and minerals. The off-gas contains mainly nitrogen, carbon dioxide and oxygen and can be safely vented to the atmosphere. The aqueous stream may be utilized as a fertilizer.

Feces mineralization in detail

When mixed with air and heated above ca. 400°C under high pressure, the feces sludge decomposes and is oxidized completely to carbon dioxide and water. This process is called “hydrothermal oxidation” or HTO. The water in the sludge does not evaporate but mixes with the air and provides a reaction environment for an efficient conversion of the organic matter within a few minutes.

We are developing a comprehensive computer model of the HTO reactor to be built for the Autarky toilet. This computer model is fed with data from experiments carried out in small autoclaves with real fecal sludge. We determined that the oxidation reaction is rapid above ca. 300°C and runs to completion within a few minutes at 400°C. The next step is to build a small laboratory-scale prototype to perform experiments under more realistic conditions and to test the model predictions. With the validated model a full-scale prototype will be designed and built in 2016.

Feces sludge before (left) and after HTO treatment (right).


Hübner, T.; Roth, M.; Vogel, F. (2016)  Hydrothermal oxidation of fecal sludge: experimental investigations and kinetic modeling, Ind. Eng. Chem. Res. 55 (46), pp.11910-11922 

Hübner, T. (2015) Hydrothermal Oxidation of Faecal Sludge, Master thesis, TU Dresden and Paul Scherrer Institut.

Vogel, F.; Smith, K.A.; Tester, J.W.;Peters, W.A. (2002) Engineering Kinetics for Hydrothermal Oxidation of Hazardous Organic Substances, AIChE J. 48(8), 1827-1839.

Mehr zu FMECA

Autarky Allgemein

Das Projekt wird im Rahmen der „Reinvent the toilet Challenge (RTTC)“ durch die Bill & Melinda Gates Stiftung (BMGF) gefördert. Ziel ist die Entwicklung einer vollkommen neuen Toilette, die ohne Anschluss an Wasser- oder Abwasserleitungen und Elektrizität funktioniert. Darüber hinaus soll sie den Nutzer nicht mehr als U$ 0.05 pro Tag kosten und ein ansprechendes Design bieten um weltweit Zugang zu sanitärer Versorgung zu ermöglichen. Autarky ist die Fortführung des Projekts Blue Diversion.

Über uns

Das Autarky-Projekt besteht aus einem internationalen Team an Forschern von der Eawag, dem Paul Scherrer Institut, der FHNW, der EPFL, der Schwedischen Universität für Agrarwissenschaften (SLU) und dem österreichischen Designstudio EOOS.

Autarky Team

Partner Projekte

Blue Diversion Toilet

Blue Diversion Toilet - eine attraktive, sichere und erschwingliche nachhaltige Sanitärlösung

Vuna-Nährstoffrückgewinnung aus Urin

NEST Projekt

Nest - Gemeinsam an der Zukunft bauen