26th Ward Waste Water Treatment Plant Upgrade
To support design upgrades to the existing Primary Settling Tanks (PSTs) of the 26th Ward Waste Water Treatment Plant (WWTP) for the New York City Department of Environmental Protection (DEP), Alden conducted a Computational Fluid Dynamics (CFD) model study to assist in evaluating the hydraulic and sedimentation performance of: 1) A new Flow Distribution Structure (FDS), 2) A new influent channel that services each PST with new ports and target baffles, and 3) New PST effluent weirs and troughs. The study included developing three-dimensional (3D) CFD models and conducting a series of simulations to verify flow and grit distributions favorable for optimal performance.
A series of FDS designs were modeled for: flow and grit distributions to each operating tank; water surface elevations at inflow chamber of FDS; water surface elevations upstream of the troughs; the relationship between the water surface elevation and flow rates; and weir setting and optimization of the FDS design. The best design was chosen for grit and flow splits.
The PST design was modeled for flow and grit distributions through ports using: various influent channel configurations; flow and grit distribution within the PSTs and performance in conjunction with the existing baffle boards, target baffles, vertical baffle wall, flow distributors, symmetrical and asymmetrical layouts of inlet piping to influent channel ports, downstream weirs and troughs; prediction of the water surface elevation in the FDS compartment; and estimation of flow and grit distributions of other PSTs. The results of the model indicated possible design improvements, which were then implemented and tested in the model. Afterwards, the PST weirs and troughs were modeled in details to ensure favorable hydraulic performance.
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Civil InfrastructureHydrology Hydraulics and Fluids
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An existing roof vent arrangement was allowing rainwater to enter the Pot Room. Alden supported efforts to develop a roof vent geometry to eliminate the intrusion of rain water. The purpose of the CFD study was to ensure that the roof vent modification did not increase pot room temperature levels beyond specified limits for workers in the plant.
To evaluate the existing and proposed Pot Room arrangements, thermal and fluid flow profiles in the immediate vicinity of the pots were determined based on air flows through the plant floor and wall mounted vents. The detailed CFD model was developed from plant drawings to include all major basement, pot room and roof venting geometries. The surrounding ambient environment was included with quiescent atmospheric conditions and average ambient temperature. Thermal losses form the pots to the pot room air and from the pot room to the environment were included in the analysis. The results of the CFD modeling showed that the proposed modification to the roof venting arrangement was acceptable and would not increase the temperature in the worker-occupied spaces by more than 2 degrees F.
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Civil Infrastructure
Smelter Pot Room Roof Ventilation System
Read how a CFD study ensured that a roof vent modification did not increase pot room temperature levels beyond safe levels
Plant McDonough, owned and operated by Southern Company, has experienced excessive siltation at the makeup water intake. The intake uses cylindrical wedgewire screening within an intake originally designed for much larger, once-through cooling water flows. Flow modeling was performed to provide a viable passive solution to reducing the sediment accumulation at the intake. To model the geometric details of the system accurately, a field survey was performed prior to the flow modeling efforts. The flow study included both CFD modeling and scale physical modeling.
For this investigation, Alden developed a 1:20 scale live bed physical model. This model was extremely well tuned to reproduce the behavior of bed load sediment. Even with the very fine crushed walnut shell particles, however, it was challenging to reproduce the behavior of suspended load. The use of a high fidelity CFD model, therefore, proved extremely useful for this project, in that suspended load is generally very accurately tracked with CFD models, which are not well validated for bed load simulation. By using the two together, the two extremes of sediment transport are captured, and developing a solution that covers this range has a high likelihood of success.
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Civil Infrastructure | Hydrology Hydraulics and Fluids
Plant McDonough Intake Modification
CFD and physical model study to assist in the evaluation of a solution to reduce the sediment accumulation.