Abstract
The purpose of this study is to evaluate the relationship between the improvement of soil permeability upon mixing with gravel-size materials and the water purification performance of a multi-soil-layering system. Focusing on the practical use of regional resources, zeolite, Sekisyu roofing tiles, Kimachi stone, Corbicula shell and bamboo charcoal, which are regional resources in Shimane prefecture, were used as gravel-size materials. Mixing these materials, especially Corbicula shell but not zeolite, with soil improved the permeability of the soil mixture layer. The calcium from the shell probably stabilized the soil structure, resulting in the high permeability. On the other hand, the high content of exchangeable sodium in zeolite probably dispersed the soil particles and decreased the permeability. Sekisyu roofing tiles had low chemical properties for water purification. The effect of Kimachi stone on improving the permeability was poor owing to the high exchangeable sodium content and its fragility. Bamboo charcoal had a high removal capacity of organic matter. The increase in the amount of outflow through the soil mixture layer enhanced the water purification capacity, especially for phosphorus. The use of regional resources enabled the improvement of the water purification capacity and is probably applicable in a multi-soil-layering system.
