The influence of wind in secondary settling tanks for wastewater treatment-A computational fluid dynamics study. Part...

Computational fluid dynamics model is used to understand the impact of wind on the performance of a secondary settling tank (SST) in a wastewater treatment plant (WWTP). Unlike most of the previous modeling studies which evaluated the wind effect on the settling tank in a water treatment plant, this study evaluates a circular SST in a WWTP at different current velocities and flow conditions. Performance indicators, such as effluent suspended solids and sludge blanket height, and three-dimensional hydrodynamics profiles are compared among different windy conditions and the calm condition and under different wind directions and flow conditions. The simulation results show that the existence of wind has strong negative impacts on the overall performance of the circular SST. The prediction of ESS is doubled in the circular SST under the mild wind condition. Moreover, the circular SST is more sensitive to the wind along the inlet port direction. PRACTITIONER POINTS: This is the first comparison of wind effects on a circular secondary settling tank Detailed computational fluid dynamics solution procedures to simulate a secondary settling tank Wind effects are investigated under multiple flow conditions, current velocities, and wind directions The performance of a circular secondary settling tank is very sensitive to the wind Wind along the inlet port direction has stronger negative impacts than it along 45° to the inlet direction.