Passive system for internal surface cleaning and homogenization in the air-lift vertical column photobioreactors

the mixing and surface cleaning performances of an air-water diffuser is tested in a 70 L air-lift bubble column photobioreactor in which single-celled Cyanobacteria Synechocystis sp. fed by sewage sludge waste is cultivated. Results have shown that a water velocity of 0.2 ms-1 in the non-aerated bottom part of the PBR and 0.06 ms-1 in the aerated zone are sufficient to prevent sludge deposition and biofouling on the surfaces. Moreover, water recirculation is observed to have an important role on the sludge mixing and algal homogenization of the photobioreactor. A computational model is then created and tuned using experimental data in order to predict the water and air velocity map in the whole domain.