The Use of Flocculation as a Preconcentration Step in the Microalgae Harvesting Process

Flocculation is a widely utilized separation technique in colloid chemistry, the chemical industry, and wastewater treatment. However, its application in microalgal biomass production and downstream processing remains limited. Biomass harvesting represents a significant cost factor in large-scale microalgae production, with the separation of biomass from the liquid medium accounting for up to one-third of total production expenses. The use of flocculants as a pre-treatment step has emerged as a promising approach to reducing these costs. Laboratory-scale flocculation is commonly employed to optimize flocculant dosage and assess strain-specific flocculation efficiencies. Meanwhile, pilot-scale flocculation, when applied before centrifugation, provides critical insights into the applicability of specific flocculant-strain combinations and their impact on yield and biomass quality. Numerous studies have investigated the flocculation behavior of various microalgal strains using a wide range of chemically distinct flocculants at the laboratory scale. This review highlights recent advancements in microalgal flocculation as a pre-centrifugation strategy and outlines future perspectives for achieving cost-effective, large-scale microalgal biomass production as a globally viable resource.