A toilet cistern contains around ten litres of water, and people tend to flush around three times per day, on average. If all 7 billion people on earth were to do this, the result would be a serious water shortage. According to the World Health Organisation (WHO), 2.6 billion people worldwide have no access to a toilet. Each year, this results in 200 million tons of raw human waste lyiang or floating around. The WHO also estimates that 1.4 million children die every year due to contamination from contact with faeces.
This is why the United Nations decided in 2011 to reduce the number of people without a toilet by half. The Bill & Melinda Gates Foundation made 42 million dollars available for the development of a toilet that could process faeces and urine without electricity, water or a sewerage system. This lead to the ‘Reinventing the Toilet Challenge’, in which a team from TU Delft is also participating: eight researchers from the Process & Energy department (Faculty of 3mE)and five from the Faculty of IDE (Design for Sustainability department).
The team’s solution consists of a toilet that separates urine and faeces from flush water, along with a toilet building and a technical plant that dries and gasifies the waste and converts it into electricity. According to the project manager Jan Carel Diehl (IDE), the most outstanding feature of the entry from TU Delft is its ability to be customised to the end-user. Other universities tend not to look beyond the technology itself.
The toilet is a perfect example of user-oriented design. It was preceded by tests and countless discussions. Ir. Anne Jansen and her colleagues put the people from India at their ease and asked them about their experiences and preferences. Which hand do you use to rinse your anus? And do you prefer to use a bottle, a hose or a bidet?
Supported by the experience of ‘toilet professor’ Dr ir. Johan Molenbroek, the current design was developed with a wide opening between the feet, a button for flushing (with half a litre of water) and a handle operating a hose to rinse the anus and bowl (always with the left hand) with another litre of water.
An ingenious dual-flap system separates the faeces and urine from the flush water. The excrement and urine drop down when someone activates the flap by pressing the flush. A special handle for the flush water moves a separate flap for the toilet opening that diverts the water into a sedimentation tank.
As much as 80% of this flush water is recycled. It is estimated that 500 litres of water are lost and 2000 litres purified in a sedimentation tank, sand filter and UV disinfection unit on the roof. After treatment, the water is good
enough for washing hands, but not