Blue Diversion Toilet

Reinvent the toilet!

To do social design, you don’t have to go to Africa!

EOOS became involved in Africa through our partnership with the Swiss water research institute Eawag, which had worked there for many years.

We certainly wouldn’t have come up with the idea of going to Africa to build toilets under our own steam. There are more than enough design problems in our immediate vicinity that are just as complex and challenging, although perhaps more manageable, given that the issues are at least embedded in a cultural context we know well. That was clearly demonstrated in our project for the refugees who arrived in Vienna in 2015. Rather than working directly with the people in need, in this project too, as in Africa, we engaged with them through NGOs.

One advantage, however, was that heading to work didn’t involve hours of flights, not to mention hairraising nocturnal cab rides on unlit streets at night thronged with people and animals. We could take the subway to the refugee shelter every day if need be. Working in informal settlements is dangerous, even with local support on the spot. We know of many cases that have ended badly. Although the team’s safety is consistently our top priority, incidents can never be ruled out completely and some risk always remains.

Blue Diversion Toilet 2011 - 2014

We are often asked how we ended up working on a project with the Gates Foundation. It was a stroke of luck that we visited Eawag, the Swiss water research institute, a few months before the call for the Reinvent the Toilet Challenge was launched and asked about ways that we could support development projects as a design studio. Project manager Tove Larsen immediately suggested something we could do, and we helped out with design concepts and visualizations for what proved to be a successful entry.

One of the projects we developed was a mobile toilet unit that can be retrofitted into existing toilet blocks or apartments. Eawag’s technical concept is based on separating material flows. Just as in the human body, urine and feces are treated in separate systems.

The toilets are shared by one or more families. The containers for urine and feces are picked up regularly and taken to a central treatment plant. There, nutrients are recovered from the urine to produce fertilizer – thanks to the VUNA process previously developed by Eawag.

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Technical diagram of the toilet: the decentralized water treatment system is located in the rear wall. Used wash water is separated via a valve and treated with special filter technology so that it can be reutilized for handwashing. Urine and feces are stored separately in containers under the squat toilet that are collected for processing.

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With the card deck we helped to develop, workshop participants could run through the service system and application scenarios.

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Meanwhile, the children were kept busy with a coloring sheet of the toilet.

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For the first field test in 2011 in Kampala, Uganda, we built a dummy version of the toilet with a local craftsman to demonstrate the principle. Project manager Tove Larsen (center) explains the water treatment process. The local Makerere University helped pick the community.

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“It’s a shame to build a house without a toilet or to come out a toilet and not wash your hand.”

Bobi Wine, Sanitation Song
EOOS field notes from Kampala, Uganda, 2011

Reinvent the Toilet Fair 1, 2012

A year after the project began, the Gates Foundation invited all participants in the Reinvent the Toilet Challenge to a presentation at its headquarters in Seattle. We were fortunate to be among the project teams that made a presentation directly to Bill Gates. On the technology front, three other projects emerged as the winners, but our entry was awarded a special prize that recognized our project’s design commitment. We had anchored the role of design in developing transformative high-tech sanitation solutions. The project’s design model stayed in Seattle and was displayed in the Foundation’s Visitor Center.

Field Test in Kampala, Uganda 2013

After another funding approval, the project team put our functional model through its paces in various contexts: first at Makerere University, then in a community center in Kifumbira, an informal settlement, and finally with an extended family in Kisalosalo. Eawag interviewed over 400 people about the toilet system and compiled a comprehensive study based on their replies.

In Kampala, we visited a local factory that manufactures water tanks using rotational molding to determine whether the water treatment module could also be made locally with this technology. A workshop with artisanal metalworkers focused on producing the support structure and metal tanks.

A small solar panel installed on the roof provided power to operate the toilet. However, this device had to be guarded at night to prevent theft. We gradually became aware of the kind of stumbling blocks our project might encounter in the real world.

Field Test in Nairobi, Kenya 2014

A more advanced model that already incorporated some industrially manufactured components was tested in Mukuru, an informal settlement in Nairobi. The engineering for the high-tech toilet was provided by Tribecraft and the field test was run with support from Sanergy. Eawag conducted sixty interviews with regular users and 300 interviews after one-off use.

The Blue Diversion Toilet was installed in one of the toilet blocks managed by Sanergy, which offers container-based sanitation in Nairobi. The Social Enterprise service team collected urine and feces from the rental toilets daily and took them to a composting plant where the feces were turned into potting soil. However, the harsh conditions in the slum quickly pushed the mechanical components to their limits. Sludge and sand clogged the valves and the separation system needed constant repairs. A software update failed due to numerous power outages and limited bandwidth. A painful reality check for the ambitious prototype after two years of development.

Blue Diversion Autarky 2014–2019

In the new post-2014 project phase, the focus is on treating flush water, urine and feces in the toilet itself. In this context, we took charge of the system architecture and design as well as constructing the toilet for families and a public handwashing station. We also continued the development process for the toilet; the Urine Trap concept separates urine in the toilet bowl—it flows over an edge and is drained out underneath. The jointly developed version was exhibited for the first time at the Reinvented Toilet Expo in Beijing in 2018.

After the trade fair in Beijing, the handwashing station and toilet were tested in Durban, South Africa, in 2019. In our urine separation toilet, a hydrocyclone separated the flush water, subsequently treated in the water treatment unit, which now had a capacity of 300 liters. Urine separated in the toilet by the Urine Trap was chemically stabilized under the toilet and evaporated. It could subsequently be manually scraped off large drying trays and used as fertilizer. The feces were not treated in this field test. Experiments with supercritical water oxidation were carried out in the laboratory.

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