Abstract:
The biomass of microalgae, especially in paste form, is crucial for aquaculture, serving as live feed and in larviculture as green water. However, harvesting microalgae presents significant challenges due to their small size and low concentration in cultures. Flocculation emerges as an effective and economical method to aggregate the cells and facilitate their separation. In this study, the microalga Tetraselmis suecica was cultivated using a modified f/2 medium in a batch system of up to 60 L, with a constant photoperiod at 22°C. Flocculation tests were conducted when the biomass reached 1 g/L, using industrial calcium hydroxide (Ca(OH)2) and sodium hydroxide (NaOH) as flocculating agents, adjusting the pH to 10.8 in each treatment. The flocculation efficiency was evaluated by measuring the sedimentation rate in a transparent 100 mL glass cylinder, recording the distance traveled by the floc over time. Flocculation with Ca(OH)2 showed a higher final harvest density and a superior sedimentation rate (p<0.05) compared to NaOH. These results indicate that calcium hydroxide is an excellent flocculant for T. suecica, as it reduces harvest time and costs, in addition to offering greater availability and fewer market restrictions.
Key words: Flocculation, microalgae, sodium hydroxide, calcium hydroxide.