Self-flocculation of enriched mixed microalgae culture in a sequencing batch reactor

Area of Science:

• Biotechnology
• Renewable Energy
• Environmental Science

Background:

• Microalgae are a promising source for sustainable biodiesel production.
• Economically viable biodiesel requires efficient and low-cost microalgae harvesting technologies.
• Self-flocculation is a key harvesting method that avoids chemical additives.

Purpose of the Study:

• To investigate the impact of reactor geometry (height-to-diameter ratio) and adaptation period on microalgae growth and self-flocculation.
• To evaluate these factors in sequential batch reactor (SBR) operations without bacterial addition.
• To determine optimal conditions for enhanced microalgae harvesting.

Main Methods:

• Six 8-L reactors were used, varying in height-to-diameter (H/D) ratios (5 and 8).
• Experiments included batch and sequential batch reactor (SBR) operations over 30 days.
• An adaptation period was introduced for specific SBR experiments, with consistent volume exchange ratio (25%) and settling time (30 min).

Main Results:

• A higher H/D ratio (H8c) significantly improved biomass productivity by threefold.
• The H8c reactor achieved 95% settling efficiency in 5 days, compared to 30 days for the H5c reactor.
• Microalgae biomass loss was reduced under optimized conditions.

Conclusions:

• A higher H/D ratio positively influences microalgae growth and self-flocculation.
• Implementing an adaptation period in SBR operation enhances microalgae harvesting efficiency.
• These findings contribute to cost-effective microalgae-based biodiesel production.