The Orange County Sanitation District (Sanitation District), under a capital improvement project, developed an automated procedure to perform acid washing on packed tower chemical scrubbers. Packed-tower chemical scrubbers operate with an alkaline solution, composed of sodium hydroxide, an oxidant, and make-up water. The make-up water may be chlorinated secondary treated wastewater or city water, which are both hard water sources and contribute to scale build up on the random pack media in the chemical scrubbers. In addition, the use of sodium hydroxide contributes to scaling on the packed media. Acid washing is necessary to maintain optimum performance within the chemical scrubber.

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The Orange County Sanitation District (OCSD) located in Southern California is in the process of building a 340-mgd headworks facility. Carollo Engineers is responsible for the design of the proposed facility. As part of the design, computational fluid dynamic (CFD) modeling was completed on three areas of the proposed headworks facility: the Bar Screen Facility Inlet Structure, the Influent Pump Station Discharge Channel/Grit Basins Inlet Channels, and the Primary Splitter Structure. Utilizing a commercial CFD model, numerical models were constructed to simulate steady-state isothermal three-dimensional (3D) turbulent flow within the selected systems. The model results were used to evaluate the relative performance of the proposed design, and make adjustments, as necessary, to improve the hydraulic efficiency of the system.

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