SEPARATION OF BUTYLTINS AND METALS LADEN SOLIDS FROM DREDGED MATERIAL FROM A DRYDOCK USING SIEVING AND MAGNETS

Abstract

Drydocks have been increasingly used for the construction, maintenance, and repair of ships, boats, and o the watercraft along the sea coast in South Korea. In a dry dock, large quantities of particulate pollutants containing antifouling paint and metallic particles are emitted into the bottom particularly during repair, maintenance and cleaning of vessel hulls. The drydock bottom is flooded frequently with seawater and the adjacent sea becomes naturally contaminated with drydock sediment. These deposited particulate pollutants pose significant health threat to the local populations who consume fish and shellfish taken from the adjacent sea area. In order to develop an efficient separation method for butyltins and metals laden solids from the excavated materials from the bottom of a drydock, we investigated selected size distribution of grains, magnetic properties of each grain size fraction, and butyltin and toxic metal contents in each size fraction were determined for the bottom sediment deposited in a dry-dock located in Busan, southwestern coast of Korea. We found that high levels of TBT occur concurrently along with high level of Cu, Zn, and other metals, and were also found to exhibit high magnetic susceptibility. The co-occurrence is probably due to the major chemical elemental components of layered paint fragments usually applied to the ship’s hull. The efficiency of magnets to separate those butyltins and int and metallic particles are emitted into the bottom particularly during repair, maintenance and cleaning of vessel hulls. The drydock bottom is flooded frequently with seawater and the adjacent sea becomes naturally contaminated with drydock sediment. These deposited particulate pollutants pose significant health threat to the local populations who consume fish and shellfish taken from the adjacent sea area. In order to develop an efficient separation method for butyltins and metals laden solids from the excavated materials from the bottom of a drydock, we investigated selected size distribution of grains, magnetic properties of each grain size fraction, and butyltin and toxic metal contents in each size fraction were determined for the bottom sediment deposited in a dry-dock located in Busan, southwestern coast of Korea. We found that high levels of TBT occur concurrently along with high level of Cu, Zn, and other metals, and were also found to exhibit high magnetic susceptibility. The co-occurrence is probably due to the major chemical elemental components of layered paint fragments usually applied to the ship’s hull. The efficiency of magnets to separate those butyltins and