The basic engineering design of large-scale factory for culture of seaweeds aimed at water purification in coastal sea area

In the coastal fields, eutrophic water owing to human activities has caused serious environmental problems such as red tide and anoxygenic water. In order to improve these problems, the large-scale factory will be installed at the mouth of river in which mass seaweeds are cultured. The seaweeds have potentiality to clarify the eutrophic water and to improve the stagnation of material cycle in enclosed sea area. However, in order to operate stably this factory, the purification ability of selected seaweeds should be clarified. In terms of capacity to absorb nutrients and ease to cultivate, some kinds of seaweed are evaluated experimentally in incubators. In the selection, we decided that Ulva prolifera is the most effective for the seaweed cultivating factory in Japan. However, it is known that Ulva prolifera can grow into the different two shapes; floating type with globular body and fixed type with long and thin body. If we design the seaweed cultivating factory using engineered approach, it is need to know quantitatively which shape is more efficiently. Therefore, the experiments are performed in order to compare the response characteristics of absorbance nutrients under the different temperature conditions. This result suggests that the cultivating of the fixed type is more effective for the seaweed cultivating factory. The results of this study enable us to design the large-scale factory for water purification in coastal sea area using culture of seaweeds.