Mercury-Contaminated Sludge Treatment by Dredging in Minamata Bayby Shinya Izumi, Ministry of Transport, Japan,
Abstract: To eradicate Minamata disease, caused by sewage containing methyl mercury accumulating in fish and shell-fish through the food cycle, a large-scale sediment disposal project was conducted with special care taken to prevent new pollution resulting from the project itself. The basic approach to sediment disposal was to construct a highly watertight revetment to reclaim the inner area of the Bay and then confine sediment dredged from the remaining contaminated area in the reclamation area through surface treatment. Before sediment disposal, boundary nets were installed to enclose the work area to prevent the mixing of contaminated and non-contaminated fish. Dredging work was successfully carried out by using four cutterless suction dredgers, newly developed in advance for minimizing muddiness due to dredging work. Sediment, discharged into the reclamation area, keeping it under water, was covered with a sandproof membrane, particularly volcanic ash earth with light-weight and mountain soil, successively.
Subject Headings: Water reclamation | Dredging | Pollution | Bays | Volcanic deposits | Sludge
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