Simulation study of rhombic pipe sedimentation structures for removal of suspended solids in urban landscape water bodies

Abstract

[Objective] Rhombic pipe sedimentation structures have been widely used for water pollution treatment in water plants and reservoirs. However, their utilization efficiency in the in-situ treatment of urban landscape water bodies polluted with suspended solids(SS) remains unclear. The aim is to explore the relationship between structural parameters and efficiency when rhombic pipe sedimentation structures are applied to water bodies with different levels of SS pollution. [Methods] Two structural parameters of the rhombic pipes—pipe diameter and pipe length—were selected, and 9 geometric models of rhombic pipes were established. Two inflow variables, SS concentration and SS particle size, were set to form five different wastewater scenarios. Computational Fluid Dynamics(CFD) software was used to conduct solid-liquid two-phase flow numerical simulations, and field tests were set up to calibrate the model-solving parameters. The rhombic pipe structural parameters were selected based on removal efficiency. [Results] The result showed that under water pollution scenarios dominated by SS concentration and SS particle size, the rhombic pipe structure with a 40 mm diameter and 2 000 mm length achieved the highest removal efficiency, with average removal rates of 87.3% and 75.4%, respectively. The removal efficiency increased with rising SS concentration and particle size in the influent. Additionally, removal efficiency exhibited a strong positive correlation with the uniformity of velocity field inside the pipes, and a moderate negative correlation with pipe clogging. [Conclusion] The result indicate that under fluctuating influent water quality conditions, the rhombic pipe structure with a 40 mm diameter and 2 000 mm length demonstrates strong stability in SS removal efficiency, validating its high potential for efficient application of rhombic pipe sedimentation structures in in-situ treatment of urban landscape water bodies.

Keywords

numerical simulation / urban landscape water bodies / rhombic pipe structure / suspended solids / removal efficiency