treatment plant (WWTP), oxidation ditches (OD) hydrodynamics to design and develop the desired
flow conditions of the WWTP. Computational fluid dynamics (CFD) models were developed using
CFD software, ANSYS Fluent (V13) with the three-dimensional, steady, incompressible flow based
on the Reynolds-Averaged Navier-Stokes equations for flow field calculations in the combined ODs.
Also, three different turbulence models [standard k–ε (ske), renormalization group k–ε (RNG), and
realizable k–ε (real)] were performed for a comparative study. The numerical model was verified based
on the experimental data in the relative errors for ske, RNG, and real 13%, 17%, and 18%, respectively.
According to the parametric studies, the hydrodynamic characteristics of the existing WWTP
were investigated. The maximum wastewater velocity occurred at the inlet and outlet, affecting the
flow field in ODs. Moreover, the water velocity decreased as it moved away from the inlet and outlet
locations at vertical and horizontal. It can also be noted that there was no homogeneous flow field
distribution in ODs. Because the current OD model needs improvement hydrodynamically, a new
original OD geometry was presented to eliminate the hydraulic weakness of existing WWTP by CFD
analysis. The new original geometry provides a more homogeneous flow field in ODs that mean it will
also help treatment efficiency and energy saving according to the operating principles of this facility.