CFD simulation of settling

Wastewater treatment plants (WWTP) treat and purify municipal or industrial wastewater, for water reuse or safe release to the environment. A critical process step is settling, in which suspended solids or precipitates get the time to sink. This allows for a separation of a sludge stream and a clean water stream. Computation Fluid Dynamics (CFD) is a powerful tool to model fluid flow in settling basins and tanks, in order to understand and improve the process. CFD is therefore valuable in many situations:

• Troubleshooting: Providing a diagnosis for operational issues like poor flow distribution, sludge accumulation, or short-circuiting. Using these insights to find solutions by changing operational conditions or adapting designs.
• Design: Optimizing the design, ensuring homogeneous distributions and appropriate settling, even before the plant is built. The design freedom will be limited by space and other economic constraints.
• Performance prediction: Forecasting the behaviour of the process under various operating conditions, and finding the maximal throughput capacity, at which e.g. excessive turbulence disturbs the settling process.

As an example, the video below shows the settling process during filling and in static conditions in a WWTP settling tank. The CFD simulation uses validated sludge sedimentation models, which can be adapted and calibrated to the sludge properties in a specific WWTP location.

Contact us to discuss the possibilities of CFD in settling and other wastewater processing steps such as:

• Aeration: Making sure air is well-distributed and oxygen levels are maintained throughout the tanks
• Distributors and pump stations: Avoiding inefficiencies such as shortcuts, preferential directions and inconsistent overflows
• Disinfection: Guaranteeing homogeneous mixing of chemicals or contact to UV light