Contained Dredgiung System as a solution for turbidity

Abstract

This thesis aims to investigate the effectiveness of the contained dredging system (CDS) in avoiding turbidity during dredging activities. Turbidity is a common issue that arises during dredging activities and causes the sediment to be suspended in the water column, which can have negative impacts on the environment. The CDS is a novel way of dredging that focuses on avoiding turbidity, and it has been developed by Hydrex, an Antwerp-based firm. The research aims to determine whether the CDS provides a solution to the environmental problems associated with turbidity at contaminated sites. The research methodology involves conducting a literature study, theoretical analysis, and real-life testing of the CDS. The main research question is ”To what extend does the CDS create turbidity?”, and a set of sub-questions is formulated to answer the main research question. Based on the analysis and findings presented in this thesis, it can be concluded that dredging activities can have a negative impact on the environment through the generation of turbidity. Traditional dredging techniques such as the clamshell, backhoe, trailing suction hopper dredger (TSHD), and cutter suction dredger (CSD) all create turbidity to varying degrees. However, methods such as silt curtains, sedimentation ponds, polymer flocculants, pH adjustment, vegetation buffers, and bio-engineering can be used to minimize the spread of sediment and reduce turbidity levels. Furthermore, new dredging techniques have been developed to minimize turbidity. The contained dredging system (CDS) was developed to minimize the negative impact of dredging on the environment by focusing on avoiding turbidity by dredging within an air chamber. However, the theoretical analysis of the CDS showed that it creates turbidity when the critical height of the dredged wall is exceeded. The CDS was designed to create no turbidity, but the theory and calculations presented in this thesis suggest that it does create turbidity. In conclusion, the CDS, although developed with good intentions, does not fulfill its requirement of not creating turbidity. The device creates turbidity due to the low critical height of the vertical wall, which will collapse after dredging. However, the CDS could still be used in non-sensitive areas or in very polluted areas where accurate dredging is necessary.