Magnetic Density Separation (MDS) is a novel method for the separation of shredded complex wastes [7, 8]. It uses a magnetically induced density gradient in a ferrofluid, which allows particles with different densities to follow different trajectories. Small variations in feeding direction, spread, and velocity can significantly affect the quality and purity of the separation. The MDS-based machine (MDX) studied in this research was developed by the Technical University of Delft and Myne Circular Metals B.V. After research on magnet configurations [9], fluid stabilization [10], fluid dynamics [11, 12], and the particle sliding phenomenon [8]. This thesis investigates how feeder geometry, vibration parameters, and material properties influence feeding performance and how this affects the separation. A Discrete Element Method (DEM) model was developed to simulate the behaviour of shredded copper cable feed as it is fed to the MDX by a vibratory feeder. The feed was modelled as a mixture of copper, aluminium, PVC, and PP/PE, represented by superquadric particles. Material properties and interaction properties were calibrated using literature and a Bulk Calibration Approach (BCA). A Design of Experiment (DoE), including a Definitive Screening Design (DSD), was used to calibrate sliding friction and restitution coefficients for all interaction parameters against three Key Performance Indicators (KPIs): discharge time, heap height, and angle of repose. The best-performing parameter set used a sliding friction of 0.8 and a restitution of 0.1, uniformly applied across all material types. The DEM simulations were validated against experimental tests, showing good agreement in mass flow but some deviation in feeding profiles. This calibrated DEM model was then used to test 20 feeder design variations across six base concepts, including straight and arced ends, varied feeder angles, the addition of particle-guiding walls, and different feeding bed interaction parameters. Feeding performance was quantified using four output parameters: horizontal and vertical insertion velocity, horizontal spread (modelled as a Gumbel distribution), and mass throughput. These were selected based on their known influence on separation purity in MDX. The results showed that higher vibration frequencies increased both feeding speed and particle spread. Arced feeder ends tended to increase forward particle velocity and spread, especially at larger radii, while the straight-ended design minimised these effects. The addition of a guiding wall helped reduce horizontal spread without sacrificing throughput. Ultimately, the best concept uses a straight end with a guiding wall to achieve low particle speeds and a narrow horizontal spread, with a throughput of 0.5 kg/s. ... Read more

This research explores the feasibility of implementing ceramic microfiltration (CMF) treatment in Maputo, Mozambique, to reclaim wastewater for industrial reuse, addressing the city's pressing water scarcity challenges. As rapid urbanization increases Maputo's reliance on potable water for industrial and agricultural needs, this study evaluates reclaimed wastewater as a sustainable alternative to alleviate demand on the city's limited freshwater resources. Using a CMF pilot plant, the project tested wastewater from the recently upgraded Infulene Wastewater Treatment Plant (WWTP) to assess whether CMF treatment could achieve quality standards suitable for applications such as cooling, concrete production, car washes, agricultural irrigation, and municipal park irrigation. Furthermore, the opportunity of scalability was tested through a water balance, while relevant stakeholders were interviewed and costs estimated to complete the feasibility assessment.

Laboratory results indicated that CMF treatment effectively reduces turbidity, chemical oxygen demand (COD), and biological pollutants like E. coli and coliforms. However, dissolved particles and heavy metals were not removed, limiting its efficacy for high-specification uses. While the treated effluent met quality standards for lower-specification applications, such as local car washes and park irrigation, it did not reach the stricter requirements needed for cooling water or concrete production. This underscores a need for process optimization, particularly through coagulation, to expand CMF's application range.

To assess sustainable water availability, a water balance analysis of the Infulene WWTP considered seasonal flows and local agricultural demands. The findings suggest that although the current water supply is insufficient during dry months, full capacity utilization and improved sewer network connections in the future could support CMF-based water reuse consistently across seasons, with potential scalability for additional users.

Economic analysis compared CMF's capital and operational costs with revenue from reclaimed water sales, showing that while considerable initial investment is required, direct piping could potentially make CMF-treated water competitively priced against potable supplies under the condition of reaching maximum treatment capacity at a scaled up CMF plant. High costs associated with truck-based delivery, however, present a barrier to adoption for potential users. Stakeholder interest was strong across industrial users and developers, though contingent on achieving cost parity with the existing water network.

This study concludes that, while integrating CMF technology into Maputo's water management strategy offers promise, challenges remain in achieving quality standards for certain industrial applications and in lowering costs. Addressing these technical and economic barriers could open avenues for CMF's broader adoption, especially with future assessments that include alternative suppliers and configurations. ... Read more