The reaction that takes place in a process tank is in a large way dependent on the internal hydraulics of the tank, irrespective of the type of tank. In some tanks mixing is desirable in others plug flow is desirable. In most tanks it is very hard to achieve either of the two. This is partially due to the fact that the area through which the fluid enters the tank is small in relation to the tank cross sectional, complex geometries and changes of fluid direction. Baffles can in some cases offer cost effective and simple solutions. This paper demonstrates how Computation Fluid Dynamic (CFD) can be used to improve process tanks performance in Iraq water treatment plant by the introduction of baffles.