Improving Clearwell Design Using Computational Fluid Dynamics

The City of Phoenix was concerned with possible short-circuiting problems at the Union Hills and Val Vista Water Treatment Plant reservoirs. Chemical tracer tests conducted by the plant personnel confirmed that the reservoirs were short circuiting and the T10/T values were 0.1. In order to alleviate the short-circuiting problems and minimize chemical disinfectant usage, baffles were added to the reservoirs. Computational fluid dynamic models were utilized to develop baffle configurations and inlet jet dissipating devices. In order to verify the predictive capability of the CFD models, field tracer data was compared with CFD simulated tracer results. The CFD data matched field tracer data within 10 percent. At the Union Hills reservoir, two baffles oriented in the east-west direction increased T10/T values of the reservoir to 0.27.