Harvesting of microalgal biomass: Efficient method for flocculation through pH modulation

Area of Science:

• * Biotechnology and Bioengineering
• * Microalgae Cultivation and Harvesting

Background:

• * Efficient harvesting of microalgae biomass is crucial for industrial applications.
• * Traditional methods like chemical flocculation can be toxic and costly.

Purpose of the Study:

• * To evaluate autoflocculation, chemical flocculants, and pH-induced flocculation for Chlorococcum sp. R-AP13.
• * To determine the most effective and environmentally benign harvesting strategy.

Main Methods:

• * Assessed autoflocculation, chemical flocculants (aluminum sulfate, FeCl3), and pH adjustment using NaOH.
• * Measured flocculation efficiency and monitored changes in algal cell surface charge.
• * Investigated the reusability of the residual medium for subsequent algal cultivation.

Main Results:

• * Chemical flocculants achieved high efficiencies (87% with Al2(SO4)3, 92% with FeCl3).
• * Autoflocculation recovered 75% of biomass within 10 minutes.
• * pH adjustment to 12.0 (from 8.5) using 40 mg/L NaOH yielded the maximum efficiency of 94%.
• * High concentrations of chemical flocculants exhibited toxicity to algal cells.
• * Residual medium after pH-induced flocculation was suitable for reuse.

Conclusions:

• * pH-induced flocculation is the most effective and non-toxic strategy for harvesting Chlorococcum sp. R-AP13.
• * This method offers a sustainable approach by enabling the reuse of cultivation medium, reducing freshwater demand.