CFD Application for Wastewater Treatment Plants (WWTP)

Posted on October 1, 2023

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In previous posts related to the application of CFD to wastewater treatment plants (WWTP), we demonstrated the particular benefit of this tool to quickly and accurately predict free surface flows through basins and influent/discharge structures. In this post, we provide another example in which CFD was used to make successful modifications to a large influent channel with numerous inlet and outlet weirs.

For the expansion of a WWTP, several aeration basins were being added to the facility. These basins needed to be connected to an influent channel which then feeds the aerated waste water to several existing clarifiers as well as two new ones. Since the flow to the clarifiers is controlled by ventilated weirs, the main concern was that evenly distributed flow be channeled to each clarifier. Normally, this is relatively easy to achieve as the height of the water in the influent channel is relatively consistent along its entirety so that the flow rate to each clarifier is simply controlled by the width of each outlet weir. However, with the addition of several new basins, and constraints on the location of the outlet weirs, there was a significant variation in the water elevation along the influent channel. This variation affects the flow over the outlet weirs.

A CFD model of the expanded facility was developed and the flow over the outlet weirs was determined for various inlet conditions. Using this model, the width and height of the outlet weirs could be adjusted until an even flow distribution to each clarifier was achieved. Again, simple hydraulic calculations would have been insufficient to obtain this type of result whereas CFD simulations provided accurate predictions with a high degree of confidence.