The microalga Pseudochloris wilhelmii was cultivated in low-cost media consisting of mixtures of seawater and wastewaters simulants. Under specific conditions, the strain was capable to grow while synthesizing good quality lipids. In fact, FAMEs composition of lipids was such to potentially permit producing a viable biodiesel. A mathematical model was developed to simulate the dynamics of biomass and nutrients concentration as well as lipid content and pH. The model was then validated by comparison with the experimental results.