Control of Sulfide Release from Bottom Sediments at Borrow Pits Using Steelmaking Slag

There are many borrow pits caused by sand mining at the bottom of the coastal sea in Japan. Borrow pits have been identified as a source of oxygen-deficient water with hydrogen sulfide. It has become increasingly important to restore borrow pits to improve the marine environment. However, large quantities of sand materials are needed to restore borrow pits. Recently, dredged materials generated by sea route maintenance have been adopted instead of sand materials. However, one problem of dredged materials is that they can be weak ground materials. Therefore, slag-mixed material made from the dredged material and steelmaking slag has been proposed. In this study, control of hydrogen sulfide release resulting from changing the hardness of the slag-mixed materials has been examined. Hydrogen sulfide release strongly depends on the hardness of the slag-mixed material. Microbial analysis indicated fewer living bacteria and the relative abundance of sulfate-reducing bacteria in the slag-mixed material compared with the dredged material. The solidification of the dredged material using steelmaking slag decreased not only hydrogen sulfide release but also dissolved iron and manganese release. It is considered that controlling the hardness of the dredged material mixed with steelmaking slag provides an effective means of sulfide release control.