  We consider a coupled physical-biological model describing growth of
microalgae in a raceway pond cultivation process, accounting for hydrodynamics.
Our approach combines a biological model (based on the Han model) and shallow
water dynamics equations that model the fluid into the raceway pond. We present
an optimization procedure dealing with the topography to maximize the biomass
production over one lap or multiple laps with a paddle wheel. On the contrary
to a widespread belief in the microalgae field, the results show that a flat
topography is optimal in a periodic regime. In other frameworks, non-trivial
topographies can be obtained. We present some of them, e.g., when a mixing
device is included in the model.
