Mixed Wastewater Coupled with CO2 for Microalgae Culturing and Nutrient Removal

Area of Science:

• Environmental Biotechnology
• Microalgae Cultivation
• Wastewater Treatment

Background:

• Microalgae are promising for wastewater remediation and biofuel production.
• Optimizing cultivation conditions is crucial for maximizing biomass and lipid yields.
• Carbon dioxide (CO2) enrichment can influence microalgae growth and physiology.

Purpose of the Study:

• To investigate the effects of mixed wastewater and CO2 concentrations on microalgae.
• To evaluate nutrient removal capacity, biomass, and lipid productivity of Chlorella sorokiniana and Desmodesmus communis.
• To analyze morphological changes in microalgae under different CO2 conditions.

Main Methods:

• Cultivation of Chlorella sorokiniana and Desmodesmus communis in mixed swine and municipal wastewater.
• Application of varying carbon dioxide (CO2) concentrations during cultivation.
• Measurement of biomass concentration, nutrient removal rates (nitrogen, phosphorus, ammonia), and lipid content.

Main Results:

• Optimal conditions (1:3 wastewater ratio, 5% CO2) yielded maximum biomass concentrations of 1.22 g L-1 (C. sorokiniana) and 0.84 g L-1 (D. communis).
• High removal rates for ammonia (>99%), phosphorus (>99%), and total nitrogen (88.05% for C. sorokiniana, 83.18% for D. communis) were achieved.
• Lipid content reached 17.04% for C. sorokiniana and 20.37% for D. communis; CO2 aeration increased intracellular particle numbers and induced solitary D. communis.

Conclusions:

• Carbon dioxide (CO2) aeration enhances microalgae tolerance to high ammonia concentrations.
• Nutrient excess in wastewater can effectively induce lipid accumulation in microalgae.
• This study demonstrates a viable strategy for simultaneous wastewater treatment and biofuel feedstock production using microalgae.