Optimization of microalgae harvesting by sedimentation induced by high pH

Area of Science:

• Biotechnology
• Environmental Science
• Chemical Engineering

Background:

• Microalgae harvesting is a significant challenge for large-scale bioproduct manufacturing.
• pH-induced sedimentation is a cost-effective and viable harvesting technique, but its application in wastewater cultivation requires further investigation.
• Chlorella sorokiniana is a promising microalgal species for bioproducts and wastewater treatment.

Purpose of the Study:

• To optimize sedimentation parameters for efficient Chlorella sorokiniana harvesting from wastewater.
• To assess the impact of optimized harvesting on wastewater quality.
• To evaluate the combined efficiency of sedimentation and centrifugation for microalgae concentration.

Main Methods:

• Response surface methodology was employed to statistically determine optimal sedimentation parameters.
• Key parameters investigated included velocity gradient, mixing time, and pH.
• Wastewater quality parameters (turbidity, color, nitrogen, phosphorus) were monitored before and after harvesting.

Main Results:

• Optimal harvesting parameters were identified as a velocity gradient of 250 s⁻¹, 10 seconds mixing time, and pH 12, yielding >97.8% harvesting efficiency.
• The optimized parameters demonstrated resilience to variations in photobioreactor effluent.
• Significant removal rates were achieved for turbidity (98.3%), apparent color (97.2%), total Kjeldhal nitrogen (94.4%), and total phosphorus (98.6%).
• Sedimentation followed by centrifugation increased microalgae concentration by approximately 123 times.

Conclusions:

• Optimized pH-induced sedimentation is a highly effective and scalable method for Chlorella sorokiniana harvesting from wastewater.
• This process offers a dual benefit of efficient microalgae recovery and substantial wastewater remediation.
• The findings provide practical guidelines for industrial-scale microalgae harvesting and wastewater treatment.