Numerical Modelling and Experimental Validation of Mechanical Separation of Helminth Eggs for Wastewater Purification

Hydrodynamics of wastewater, which is contaminated with helminth eggs is computationally and experimentally investigated, for laboratory conditions and for a small sewage treatment plant. In the computational analysis, the flow is mathematically modelled within the framework of a Eulerian–Lagrangian framework, where the continuous water phase is treated by an Eulerian, and the discrete particle phase (helminth eggs) is treated by a Lagrangian formulation. For turbulent flows, the Shear Stress Transport model is used to model the turbulence of the continuous phase. The effect of the latter on the discrete phase is modelled by a discrete random walk model. In modelling the momentum exchange between the phases, a special emphasis is placed upon the accurate determination of the drag coefficient for the helminth eggs. For this purpose, flow around individual eggs is analysed and laboratory measurements of other authors are inspected. Before applying these results, measurements are performed on a small sewage treatment plant using surrogate spheres, for validating the remaining aspects of the Eulerian–Lagrangian hydrodynamics modelling. Subsequently, the operation of the small sewage plant is analysed for wastewater containing helminth eggs for its optimization.