There are various methods available for microalgae separation from aqueous media. However, the combination of techniques has recently proved to be more efficient. The present study employed an integrated approach of combining three conditioning techniques including pH modulation, sedimentation, and dissolved air flotation for microalgal harvesting. A complete factorial design showed that pH value of 11 and sedimentation time of 24 h along with dissolved air flotation under operational conditions of pressure of saturator 5.7 bar and air-saturated water flow rate of 200 mL.min-1 were optimum conditions resulting in a harvesting efficiency of 70.54±0.86%. Particle size distribution analysis revealed that two floc size intervals of 4.447-5.477 m and 43.968-54.149 m, representing single and aggregated cells, are dominant in the treated solution, respectively. However, a similar floc size pattern was observed at different pH and sedimentation times, indicating that post-cultivation treatment, i.e., pH modulation and sedimentation, played no role in the formation of large-size flocs. It solely improved the efficiency of dissolved air flotation harvesting through concentrating microalgae suspension. At optimized pH and sedimentation time, the biomass concentration reached 3.65±0.18 gDCW.L-1 from the initial value of 2.37±0.05 gDCW.L-1. Growth-associated particle size distribution analysis demonstrated that cell aggregation and floc formation took place during cultivation (not post-cultivation) that was due to the shift in carbon source that, in turn, induced pH increase and autoflocculation.

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