The well documented “Urine Diverting Toilet Bowl” (UDTB) developed in 2010 by Peter Arndt from the EcoSur network in cooperation with the Clay House Project of Namibia, is undergoing a Major overhaul. After several design improvements over the years, a perfected version is now prepared to be produced industrially.
Background about dry sanitation
Human beings are producing about 50 kg feces and 500 liters of urine annually. That’s why pit latrines and compost toilets usually receive too much liquid. The high quantity of liquid does not allow a composting process, but causes a foul, putrid rottenness with an unpleasant smell coming to the surface. Faeces, when separated, are very useful as compost and urine are valuable fertilizers on their own. But in combination rottenness destroys these values and causes ground water contamination. That is why the whole dry toilet issue always goes around the question “How to reduce the quantity of liquid?”
At the upper-level market (Europe etc.) there are several options and solutions available, several of them being interpretations of our original otji toilet. They go from a filtrating process over chemical procedures up to heating systems for increased evaporation. For the low-cost market, the options are rare and often uncomfortable.
The urgency to separate the urine
A simple system which can separate solids from liquids without requiring high investments or special procedure by the users is needed. Experience shows that dry toilets are often misused to dump rubbish, therefore it must be able to handle different objects like condoms, tampons etc. So, the system should not be too sensitive, but robust enough to handle some “foreign objects”.
A user-friendly Urine Diverting technology
Our first design was for a toilet bowl which separates liquid (urine) from solid (feces), a Urine-Diverting-Toilet-Bowl. The urine flows into a pipe and is guided away. This toilet bowl is useful for any type of dry-toilets, whether compost-toilets or pit latrines. At this bowl, the urine runs down the walls and then spills into a channel out of the reach of the solids, which fall straight down. The invention is based on the fact that adhesion is stronger than gravity and keeps the urine running down the specially shaped wall, instead of dropping down vertically.
Our first UDS-Design with 20mm horizontal outlet (2010)
Social acceptability
Most Urine-Diverting-Toilet-Bowls utilize a partitioned toilet bowl for separation of urine and faeces. However, these technologies are challenging, as the dividing wall is visible, and men are getting sometimes even in physical contact with that wall, while sitting. But the partitioned toilet bowl always requires a sitting position whenever using it. This requirement has led to a low level of social acceptance and has therefore prevented urine diversion technologies over decades from a wider spread. Our UDTB has no visible obstacles and even in standing position a part of the urine is separated. It looks like a standard toilet bowl and does not imply any special requirements on the user. It is extremely user friendly and easy to clean and maintain.
Double Otji Toilet
No solid-liquid cross contamination
As many urine-diverting systems are used to collect urine for further processing into fertilizer, cross contamination must be avoided. But in order to maintain proper urine-flow, the solids may not enter the urine pipe.
Our new model has improved this separation and prevents cross contamination by keeping a horizontal distance between dropping edge and catching funnel. The funnel has a catching edge which is not straight vertical underneath the dropping edge. But this catching edge is 10 mm outside the vertical fall line underneath the dropping edge. Over the years this concept has proved to be very efficient in avoiding cross contamination.
Otji Toilets at a school in Namibia
Our new UDS-Prototype currently in development (2025)
The plaster modelwill now undergo a 3D-Scann. After digital polishing a 3D-print will be made before serial production will begin.
Links to our continued work around dry sanitation:
El inodoro seco es la solución - EcoSur: Tejas de Concreto, Cemento Puzolánico, Adobe, EcoMateriales