Rural Latrine Systems, a Pilot Project in the Ryukyu Islands

A latrine system has been modified for rural use in the Ryukyu Islands. The latrine features a shallow, ¾-inch water seal and can be flushed with 1 to 2 liters of water. The three-tank system has a normal liquid capacity of 1,850 liters (approximately 500 gallons). Tanks are precast concrete produced in the past as a village cottage industry to store rainwater collected from building roofs. The system, as innovated, provides a high degree of treatment. Suspended solids are reduced 96 percent, and coliform counts are decreased approximately 99 percent. In selected semitropical areas, this latrine offers advantages over the night soil receptacles usually used. The system is adaptable to variable site conditions. The number of tanks may vary, and the terminal portion may be either an oxidation pond or a drainage field. The system can be constructed by the home-owner, with the help of neighbors, in 40 to 60 hours. Cost for materials in the Ryukyu Islands was US$125, excluding the shelter.