Effect of inlet and outlet baffle position on settling tank performance using experimental investigation and CFD modelling

Abstract

Settling is an important unit operation in water and wastewater treatment plants. The objective of this work is to study the effect of inlet and outlet baffle positions (longitudinal and vertical) on the hydraulic characteristics of the settling tank using flow through curve method (FTC). The hydraulic performance of the settling tank was also modelled using computational fluid dynamics (CFD). The use of inlet baffle at the optimum position is significantly improved the settling tank performance in terms actual residence time and presence of dead zones. The optimum inlet baffle position is 5% of the tank length (L) from the inlet and 67% of tank depth upward from the bottom. The use of outlet baffle at the optimum position also improved the settling tank hydraulic performance. The optimum position of the outlet baffle is at 15% L from the outlet and 16% of tank depth upward from the bottom. Effect of inlet and outlet baffle positions on the velocity and kinetic energy were studied using CFD modelling. Significant reduction in dissipation of kinetic energy and reduction of velocity magnitude at the tank inlet due to the use of inlet baffle are proved by CFD modelling.