Optimization and synergistic enhancement of microalgae productivity in laboratory raceway ponds via co-regulation of automated light-supplemented mixers and electric field system

Area of Science:

• Biotechnology
• Algal Cultivation
• Bioreactor Engineering

Background:

• Raceway ponds struggle with low biomass productivity due to poor mixing and light distribution.
• Phototrophic cultures in these systems are inherently dilute, limiting efficiency.
• Optimizing gas-liquid mass transfer is crucial for microalgae cultivation.

Purpose of the Study:

• To enhance microalgae biomass production and carbon fixation in raceway ponds.
• To investigate the combined effects of light-supplemented mixers and electric field treatment.
• To improve mixing efficiency and light utilization in controlled bioreactors.

Main Methods:

• Computational fluid dynamics (CFD) simulations to optimize mixer design (75° inclined blade, 300 rpm, counterclockwise).
• Application of electrostatic field stimulation (0.6 V cm⁻¹ for 1 hour daily) during logarithmic growth.
• Laboratory-scale raceway pond experiments (71.4 dm³).

Main Results:

• Reduced dead zones from 15.5% to 1.1% and light-dark exposure to 2.7 s.
• Achieved a 20% increase in Limnospira fusiformis productivity.
• Increased maximum carbon fixation rate by 43% (to 0.14 g L⁻¹ d⁻¹) and phycocyanin by 14.4%.

Conclusions:

• The novel raceway pond system effectively enhances mixing and light utilization.
• Combined light-supplemented mixers and electric fields offer a scalable strategy for high-value microalgae production.
• This approach improves overall efficiency and yield in controlled microalgae cultivation.