Computational fluid dynamic modelling of wastewater ponds to improve design

Wastewater ponds are a popular treatment alternative in Australia, especially in the meat industry. However, increasingly stringent Australian environmental legislation is raising questions about the continued viability of ponds. Traditional design methods do not address the hydrodynamic problems (i.e. short-circuiting) nor can they predict the effects of measures like baffles or repositioning inlets or outlets to improve performance. This is because the microscale interactions between the fluid and solids, and the biological reactions are ignored. This paper presents a tool -- computational fluid dynamic (CFD) modelling and explores its potential as a new design tool for wastewater ponds. FIDAP, a finite element CFD program, is one of the new generation of commercial CFD packages available. This program has been used to qualitatively investigate the hydrodynamics of four pond systems. These models are limited to 2-dimensional (D), steady-state simulations in a laminar flow regime. They form the first step in the process to address the microscale fluid flow, mixing and biology in wastewater ponds. Considerably more modelling and validation work is yet to be done.