NEW TECHNOLOGY OF MECHANICAL TREATMENT OF DREDGED MATERIAL FROM HAMBURG HARBOR

Harbours and water ways can only fulfil their commercial task if there is always sufficient water depth for navigation. Environmental proble ms have started to influence dredging methods in recent decades. As a logical consequence of a policy giving high priority to environmental protection, Hamburg built the METHA plant (Mechanical Treatment of Har bour Sediments). METHA produces a clean sand product (grain size > 63 mu m) which is reused and a contaminated silt fraction (grain size < 1 50 mu m) which is disposed presently. Previous investigations showed t hat the content of heavy metals and organic contaminants are primarily governed by the grain size. In 1995 Strom- und Hafenbau started a new investigation to produce a further fraction from the METHA silt which can be reused. The result of laboratory- and pilot-scale research sho wed the possibility of a further separation at 20 mu m grain size. The best result was reached through a two-step separation made by hydrocy clons and spirals. The produced fraction (20-150 mu m) is mainly quart z material with a low level of contamination. In February 1996 Strom- und Hafenbau decided to built a test plant in a technical scale. The c apacity of the test-plant is 50 t/h based on dry substance The technic al concept is integrated into the METHA concept. All aspects of techni cal feasibility, economy, environment and product reuse will be invest igated in the test plant. The results of the early test phase will be presented. (C) 1998 IAWQ. Published by Elsevier Science Ltd.