Variability in raw water quality can be challenging for a utility to maintain treatment performance standards, especially with multiple raw water sources. A new raw water manifold facility was designed as part of a plant improvement project to provide the operational capacity needed to convey two source waters, either separately or blended, and distribute the flow to four new raw water ozone contactor basins. Based on historical water quality data and treatability testing conducted as part of the conceptual engineering phase, raw water ozonation was identified as a preferred approach to mitigate taste and odor events in the raw water. The raw water manifold facility includes above-grade piping, flow control valves, and mixing nozzles to provide additional motive energy for blending the source waters. Computational Fluid Dynamics (CFD) modeling was used to evaluate the distribution of flow from the two raw water sources to each online contactor, and to analyze the uniformity of the blended source waters as it enters the ozone contactor basin. The analysis was performed at variable source water flow rates and mixing water injection rates to guide design of the mixing water provisions. The ideal result was a proportional distribution of the sources at the entrance to each contactor. The analysis demonstrated the value of using CFD modeling to optimize the design and achieve project goals which provided sufficient mixing energy and avoided a conservative design that would require more mixing energy than necessary.
