Abstract
We carried out substantiative tests to investigate the effectiveness of the technique using granulated coal ash (GCA) for sediment remediation in the hypertrophic inner harbor that scum (floating sediment clusters) and malodors occur. After applying the technique, it was confirmed that large amounts of scum were decreased, indicating that the technique has effectiveness on the sediment remediation. However, the subsidence of GCA layer occurred temporally. As a result, up to 80 cm of sediment accumulated on the GCA layer. Based on laboratory experiments of the grab bucket method, GCA with larger grain size has faster setting velocity which caused a larger intrusion thickness of GCA into sediment layer, leading to the decrease of the effectiveness of the technique. It was found that the effectiveness decreased when more than 20 cm of sediment accumulated on the GCA layer. We have proposed the most effective method for construction of GCA layer by the following procedures: 1st layer of fine GCA, 2nd layer of coarse GCA, 3 times of sprinkling GCA to construct the 3rd layer of GCA after the end of the subsidence of the 2nd layer of GCA.
