This thesis explores the measurement of low sediment concentrations in pipeline flows, a critical issue in deep-sea mining. The study aims to identify and validate a continuous measurement method capable of accurately detecting suspended sediment concentrations between 10-75 g/L. These measurements are essential for minimizing the environmental impact of sediment plumes generated by mining operations.

The research begins with an analysis of material properties and flow dynamics, emphasizing the role of sediment particle size, and density in influencing suspension and settling behaviours. Highlighting the differences between concentration measurement and density measurement and the additional error involved. A review of flow regimes, turbulence, and their effects on sediment distribution within pipelines sets the foundation for understanding the complexities of representative sampling.

The thesis evaluates a range of measurement methodologies against criteria such as accuracy, range, spatial and temporal resolution, safety, cost, and impact on the flow. Optical, acoustic, conductivity, and radioactive source sensors were unsuitable due to limited range, low accuracy, or safety concerns. Promising alternatives include the U-loop, Coriolis, and vibrating fork sensors. The U-loop offers good accuracy and range, but causes significant pressure drops. Coriolis sensors provide excellent accuracy and broad range, but require careful sampling to ensure reliability. The vibrating fork sensor is simple and has a good range, but suffers from low accuracy and limited spatial resolution.

A key aspect of this research is the experimental setup, which integrates multiple sensor technologies in a controlled flow loop environment. Detailed methodologies for sensor calibration, installation, and data collection ensured the testing conditions. Tests are conducted under varying sediment concentrations, sediment types, grain sizes, and flow velocities to validate the accuracy and reliability of each measurement method.

The results reveal significant differences in sensor performance across test conditions. Test variables such as sediment type, concentration, and flow velocity are shown to influence sensor performance.

In conclusion, suspended sediment concentrations from 10 - 75g/L can be measured accurately using a Coriolis sensor. This sensor directly measures density which can be converted into concentration with minimal calibration or correction, demonstrating superior accuracy and precision across diverse flow conditions. Although it reliably detects finer deep-sea sediment, minor challenges remain when measuring coarser materials, such as nodule fines. Overall, the findings contribute to the development of environmentally responsible deep-sea mining practices, by facilitating real-time and accurate sediment monitoring.