Sedimentation through gravity is the most usual method of harvesting microalgal biomass from wastewater treatment plants. This is because of the large volumes handled and the low commercial value of the biomass formed (Munoz and Guieysse, 2006). The density and diam­eter of the cells influence the speed of sedimentation. The collection of microalgae by sedi­mentation can be carried out in sedimentation tanks (Uduman et al., 2010). However, this method can only be applied to large-cell microalgae (>70 gm) such as Spirulina. Flocculation is usually used to increase the efficiency of sedimentation (Chen et al., 2011).