Solar versus Non-Solar Urine Diversion Dehydration Toilets—Evaluation of Temperatures inside the Vaults of Different UDDT Systems

The Urine Diverting Dehydration Toilet (UDDT) is one of a wide range of technologies Ecological Sanitation (Ecosan) offers. A commonly used type is the so called solar UDDT, constructed with inclined vault doors or panels which are usually made from black iron sheets to increase the temperature inside the vaults and therefore would facilitate dehydration and hygienisation. The study aims to give recommendations on the most appropriate system by comparing solar and non-solar UDDT systems. Existing building standards for UDDTs were reviewed, 133 UDDT sites visited and a comparative temperature study of the temperature inside the vaults of different UDDT systems carried out. The temperature study needed to assess if solar UDDTs would actually succeed in raising the temperature inside the vault. Programmed temperature loggers were placed in the vaults of solar and non-solar UDDTs. The review of building standards showed that the system recommended most is the solar UDDT. The field visits identified a number of problems related to the construction of solar UDDTs. The temperature study showed that solar UDDTs do not necessarily increase the temperature inside the vault significantly and therefore are not speeding up dehydration and pathogen destruction. The study hence concludes that before a solar UDDT system is chosen the climatic conditions have to be assessed carefully. The recommended standard design should be a non-solar UDDT system. It is hoped that the study will facilitate a move towards the construction of non-solar UDDTs.