Harvesting Microalgae: Overcoming the Bottlenecks in Microalgae-Based Wastewater Treatment Through Industrial-Scale Gravity Sedimentation and Thickening

Microalgae culture is currently receiving considerable attention for its potential in wastewater treatment and production of algal biomass from which high-value bioproducts and bioenergy can be obtained, as well as the consequent carbon dioxide sequestration via the photosynthesis process. However, biomass harvesting is one of the bottlenecks in the culture and microalgae-based wastewater treatment systems. Energy-intensive technologies are required to separate the solid and liquid phases due to the low density of microalgae. Low-cost processes, such as sedimentation, are not efficient enough due to the low settling velocities of the microalgae. Sedimentation coupled with coagulation and flocculation has been widely studied on a lab scale in order to increase the microalgae settling velocity. However, only a few studies have addressed the scaling up of these experimental results to industrialize the process. In this chapter, issues of scaling up gravity sedimentation and thickening systems for microalgae culture at demonstrative or full-scale were addressed, including techno-economic analysis.