Influence of re-circulation dredging on fluid mud dynamics in seaport emden

Influence of re-circulation dredging on fluid mud dynamics in seaport emden

Gebert, J. (TU Delft Geo-engineering)
van Rhees, Floris (Deltares)
Shakeel, A. (TU Delft Rivers, Ports, Waterways and Dredging Engineering)
Kirichek, Alex (TU Delft Rivers, Ports, Waterways and Dredging Engineering)
Habdank, Janis (Niedersachsen Ports)
Amman, Baerbel (Niedersachsen Ports)

2022

Maintenance of the nautical depth in the seaport of Emden, Germany, is achieved by re-circulation of fluid mud using a trailing suction hopper dredger. Continued re-circulation has proven to maintain low settling rates and to keep yield stresses of re-circulated fluid mud below 50-100 Pa, in combination with densities of 1.15- 1.2 t/m³ enabling safe navigation through these layers. It is assumed that low-density extracellular polymeric substances (EPS), produced by a highly adapted microbial community, are responsible for the desired effect of keeping fine-grained sediment in suspension and that the regular contact with the oxygenated water phase during recirculation dredging supports thriving of this community. Climate change models have indicated increased future discharge of fresh water from the hinterland into the saline port of Emden. It is hypothesized that increased freshwater discharge alters the composition and activity of the microbial community and hence changes the prerequisites for maintaining the currently favourable properties of fluid mud. In this paper we evaluate this hypothesis by elucidating the main factors governing the success of the current practice of re-circulation dredging in the Port of Emden by means of field and laboratory investigations. Initial results obtained in this ongoing research suggest that the low yield stresses of fluid mud in the Port of Emden are not the result of a specialized microbial community producing high concentrations of EPS, but can be solely attributed to a reduction in density as achieved by re-circulation dredging. Secondly, it appears that future possible increases in the share of freshwater do not affect the sediment’s rheological response, settling behaviour and concentration of extracellular polymeric substances and will hence not adversely impact the maintenance of the nautical depth.

Re-circulation dredging
microbiology
salinity
fluid mud

http://resolver.tudelft.nl/uuid:b0795f66-18f4-4d2f-a2fe-b789dd0dd7ab

2023-07-01

Proceedings to WODCON XXIII

WODCON XXIII, 2022-05-16 → 2022-05-20, Tivoli Hotel, Copenhagen, Denmark

Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

conference paper

© 2022 J. Gebert, Floris van Rhees, A. Shakeel, Alex Kirichek, Janis Habdank, Baerbel Amman