Force acting on a submerged beam near the inlet of a biological reactor in wastewater treatment

Abstract

Design of the aerated basins in wastewater treatment includes the mass balance based biokinetic simulations, hydrodynamic calculations utilising computational fluid dynamics as well as mechanical simulation through fluid–structure interactions. Computational fluid dynamic simulation is able to resolve the flow field more accurately, producing information on velocity and pressure field within the reactor. The Reynolds Averaged Navier-Stokes formulation of momentum equation with turbulence closure equations are solved numerically with finite volume method. By knowing the flow field, the force acting on surfaces of matters could be calculated and this force as an exterior source term (or in other words, boundary condition) could be the initial setup for a stress simulation for the element. Submerged beams are applied in attached growth wastewater systems in order to provide a surface, where the biofilm carrier could be hanged. These beams bear the load of the biofilm carrier matter and the biomass developed on the surface. These are relatively static loads. Wastewater discharge has a diurnal pattern and expose a transient discharge, resulting variable (dynamic) load on the beam. In this research this water flow variation - Q(t) is linked to force variation - F(t) acting on beam will be calculated. The stress distribution is determined at five different loads (the simulation is steady-state, the scenarios are in different loading states) and as a result the tension is calculated and test for bulking is to be performed. In this research the importance of the one-way fluid-structure coupled models are highlighted.