Harvesting, Thickening and Dewatering Processes

Microalgae harvesting is an essential process for the production of almost all types of microalgae products. However, these harvesting, thickening and dewatering processes have a significant cost, despite extensive research efforts for cost reduction. Microalgal harvesting is especially challenging because these unicellular cells are small and have a similar density to water, and because the biomass concentration in culture is relatively low. The microalgal biomass (0.05% w/w) needs to be concentrated to a paste with 15-25% water content. This process is usually conducted in a multi-step scheme by primary concentration, thickening and dewatering of the biomass using a combination of various technologies. The most important implementation criteria are to avoid any biomass contamination, minimize any influence on biomass quality, and to allow water recycling to reduce the water footprint. This chapter gives an overview of several primary harvesting, thickening and dewatering methods with a focus on their advantages for implementation into a microalgae harvesting strategy.

Keywords: Harvesting, Recovery, Dewatering, Primary concentration, Coagulation, Filtration, Membrane, Centrifugation, Separation, Sedimentation, Flotation, Skimming, Thickening, Microalgae, Biomass.