Suspensions, Sludges and Soils

CEGM2000 will not be offered in academic year 2025-2026

Sediments and sludges are mixtures of mineral clay, organic material and water. Sediment and slurries are dredged for port maintenance purposes. Sludges found in (waste)water treatment plants are stabilized and dewatered for resource recovery and/or incineration. Some of these slurries/sludges are used in engineered constructions like dikes. In this module, the biochemical and physical properties of sediments and slurries will be reviewed. The way to assess their properties will be studied from the aqueous phase to the solid phase. The module consists in lectures, group assignments and practical work (lab/in-situ).

Learning Unit 1: From Suspensions to Slurries

EC: 4

Weeks: 1-3

The microscopic/mesoscopic properties of clays and organic matter will be reviewed from the point of view of colloid science. The flocculation of particles in combination with different environmental conditions will be studied and modelled. The properties of slurries in terms of settling thickening, rheology and consolidation will be measured and modelled, as function of composition and environmental conditions.

List of key topics (Elements of Learning Unit):

- Nature of clays (mineralogy) and clay properties

- Nature of organic matter and sludge (origin, composition, stability)

- Interfacial properties of colloidal particles (surface charge, Derjaguin Landau Verwey Overbeek (DLVO) theory, polymers),

- Living organic matter interactions with clay and sludge

- Flocculation, coagulation

- Rheology of slurries

- Settling, thickening, dewatering and consolidation

Laboratory experiments and measurements to determine the following properties:

- particle size distribution

- surface charge

- settling rate

- coagulation/flocculation

- rheological properties

- conductimetry

- capillary suction time

- compressibility

- biodegradation of sediment organic matter (SOM)

- methane potential of sludges

Learning Unit 2: From Slurries to Soils

EC: 3

Weeks: 4 - 6

This unit addresses the changes that sediment properties undergo during post dredging treatment and ripening on land. Students will understand and be enabled to engineer the coupled processes of physical, biological and chemical ripening which transform sediments from saturated, soft, anaerobic material to an unsaturated, well-structured and aerated soil fit for use as earthen construction material. Students will understand the associated environmental impacts, for example, related to sediment contamination or degradation of their organic components and the benefits related to sparing excavation of natural soil resources for construction purposes.

List of key topics (Elements of Learning Unit):

- Mechanical/physical, chemical and biological ripening processes

- Methods and criteria to assess physical/mechanical, biogeochemical and biological stability of sediments and soils

- Carbon cycling in the sediment-to-soil process

- Environmental behaviour of conditioned slurries

- Beneficial use of conditioned slurries and sediment

Laboratory experiments

- geochemical processes during ripening

- biodegradation of organic matter

- redox potentials

- basic soil physical/mechanical and geochemical properties

Learning Unit 3: In-situ Characterization of Sediments

EC: 3

Weeks : 6-8

The student will learn to use the methods and equipment to monitor the important properties of mud in a natural environment. These properties are assessed for mud in the water phase as well as on land. These methods will be connected to the knowledge acquired in Unit 1 and 2.

List of key topics (Elements of Learning Unit):

- Monitoring of suspended sediment (submersible laser-diffraction, camera, optical back-scattering equipment, Acoustic Doppler current profiler)

- Acoustic methods used for navigation in ports and waterways

- Determining in-situ density and flow properties of slurries

- Electromagnetic and seismic methods for monitoring of soils and fluid waste repositories