"UD Dry Toilet" Project Team Consisting Primarily of KU Faculty Members Receives Japan Water Prize (Grand Prize) (April 5, 2012)
Demonstration of a portable UD dry toilet at a care facility
Consisting primarily of Kyoto University faculty members, the "Urine Diversion (UD) Dry Toilet" Project Team (leader: Professor Yoshihisa Shimizu, Graduate School of Engineering) was awarded this year's Japan Water Prize. The group won the prize for developing a collapsible toilet unit, which can separate night soil without using water, and introducing it in areas afflicted by the Great East Japan Earthquake.
The "UD Dry Toilet" Project Team started its activities soon after the Great East Japan Earthquake with a total of thirteen members, including Associate Professor Hirohide Kobayashi, Assistant Professor Hidenori Harada and Assistant Professor Ayako Fujieda from the Graduate School of Global Environmental Studies, as well as Associate Professor Tomonari Matsuda and Associate Professor Nagahisa Hirayama from the Graduate School of Engineering. The team was able to build on the research results they had accumulated in developing countries concerning night soil separation and treatment.
The Great East Japan Earthquake on March 11, 2011 caused devastating damage to communities along the Pacific coast in the Tohoku and Kanto regions. A total of 240,000 houses were entirely or partially destroyed, while 8 million houses were affected by blackouts and 1.8 million houses were faced with an interruption in the supply of public water. At most, more than 400,000 people were evacuated to more than 2,000 evacuation centers. While relief supplies such as water, food, medical drugs, blankets and clothing were delivered from all other parts of the country, there was a lack of sufficient preparation with regard to toilet equipment, which was not considered a priority issue. Without access to conventional flush toilets, many evacuees were forced to contend with an unsanitary environment, which turned out to be a great problem for them.
To remedy such conditions surrounding the use of toilets in the wake of the Great East Japan Earthquake, the project team developed and introduced in the afflicted areas stand-alone dry toilet units capable of separating night soil. The toilet units can be used by placing them not just on the floor but also on top of existing Western- or Japanese-style toilet seats in evacuation centers, temporary houses and other places during the period before the water supply and sewage system are fully restored, thereby mitigating environmental burdens.
Prior to developing the toilet units, the team members surveyed commercially available temporary toilet systems and found that all of them used a coagulating agent to solidify the excreted night soil, requiring disposal of heaped-up waste on a daily basis, which would increase the burden on affected areas. The new toilet units, by contrast, can easily separate night soil so that urine free of pathogens may be discharged into a river or soil after removing contaminants (nitrogen and phosphor) through sedimentation, while feces may be disposed of in a sanitary manner after they are alkalized by being blended with a mixture of calcium hydroxide and rice-hull charcoals and later dried.
This year, the Japan Water Prize Committee (honorary president: Prince Akishino; chair: Director Mamoru Mohri from the National Museum of Emerging Science and Innovation) selected the grand prize winner out of 176 candidates.