CFD unlocks hidden efficiencies in wastewater mixing
With rising operational costs and stringent environmental targets to meet, increasing water and wastewater treatment efficiency is critical for plants worldwide. Optimizing operations has never been a greater priority to save costs, reduce energy consumption and cut downtime. When it comes to mixing, advanced 3D modelling is changing the game. Lars Uby, Distinguished Engineer, Mixing and mass transfer specialist, at Xylem explains the importance of computational fluid dynamics (CFD) and how to avoid the most common problems in treatment applications.
CFD is a specialised branch of fluid mechanics that employs numerical methods and algorithms to analyse and predict fluid flow behaviour. It enables the simulation of fluid flow and this advanced modelling can identify issues or inefficiencies that may arise after installation of a wastewater treatment system. With CFD, operators can be confident they are making data driven decisions on their mixing system to get the performance and results they need day-to-day and for the longer term.
The importance of CFD
The CFD process allows a plant to test various designs, flow conditions, air loads and operation scenarios digitally. This means treatment system designs can be refined on screen before creating physical prototypes and progressing to the build. It can reduce the time and cost associated with traditional trial and error approaches. When it comes to established plants, it’s revolutionised the troubleshooting and optimisation process. Ultimately, this predictive capability leads to reduced risk and optimisation of treatment equipment, process performance and cost.
Importantly for many plants, CFD can significantly improve sustainability by helping optimise energy use and reduce emissions. Through scenario modelling, CFD analysis helps identify areas of the mixing process where energy losses occur and areas where energy efficiency performance can be enhanced.
Real world examples
CFD has been around for several decades and to date it has played a vital role in supporting thousands of plants worldwide solving operational challenges and boost efficiency.
From demonstrating the feasibility of a mixing solution to how to overcome flow obstacles and improve unexpected system behavior, CFD is a powerful tool in wastewater treatment design. One example of this is a project at a plant in Sweden. The operating team turned to Xylem for help optimizing the flow in a tank with multiple supporting columns. Using CFD analysis, the team was able to accurately evaluate the design and provide data-backed recommendations on how to optimally position mixers and reduce the risk of sedimentation.
Recipe for success
The true power of CFD is realized when the process is combined with lab and application expertise. Lab testing provides important data input, insight and validation for the development of CFD methods. Extensive application expertise is essential to guide the design and CFD process, enabling the avoidance of known pitfalls.
At Xylem we pioneered the use of CFD for wastewater applications back in the 1990s. Over time, with our specialized team of engineers, we’ve streamlined the process to deliver the optimal solution. This is alongside continued investment in computation capacity and the lab to continuously enhanced our existing models.
There’s no doubt that CFD has transformed water and wastewater treatment – and its capabilities are only going from strength to strength. It helps operators avoid treatment problems, while maximizing energy and capital efficiency. It’s time to put CFD firmly in the spotlight.