Granulated Coal Ash – used Method for Remediation of Organic Matter Enriched Coastal Sediments

Fukuyama inner harbor is an enclosed bay located in the western Seto Inland Sea of Japan. This area has many serious problems, such as outbreak of malodorous gas, raw scum, eutrophication and blue tide. The purpose of this study is to propose a valuable method for remediation of organic matter enriched coastal sediments using granulated coal ash (GCA) for the restoration of water environment in the bay. Field experiments were carried out to evaluate the suppression of nutrients, malodorous gas, and raw scum by GCA, as well as to understand the restoration of biological environment. Covering layer of GCA on the sea bottom sediment of the harbor was constructed by a crane ship. Three experimental sites (each 1800m2) were constructed with different GCA layers (70 cm, 50 cm, and 30 cm) and a control site was established. The improvement effects of covering layer made by GCA were evaluated by field observations. The number of outbreak of raw scum on the water surface decreased after covering GCA on the bottom sediment. It was also confirmed that the concentration of malodorous components gas of the experimental sites was lower than that of the control site. These suggest that GCA has a capability to reduce the malodorous components and raw scum. From our findings, it can be concluded that GCA covering work is valuable for improving water and sediment environments in the bay. And it provides an effect method to mitigate the organic matter enriched coastal sediment problems.