Increased microalgae growth and nutrient removal using balanced N:P ratio in wastewater

Area of Science:

• Environmental biotechnology
• Renewable energy production
• Wastewater treatment

Background:

• Microalgal cultivation in wastewater offers a dual benefit: efficient nutrient removal and biomass generation for biodiesel.
• Simultaneous achievement of nutrient removal and biomass production is crucial for sustainable biodiesel.
• Wastewater effluent serves as a viable medium for microalgal growth.

Purpose of the Study:

• To determine optimal conditions for microalgal cultivation in wastewater for nutrient removal and biomass production.
• To investigate the impact of carbon sources, N:P ratio, and hydraulic retention time (HRT) on microalgal performance.
• To enhance lipid productivity and nutrient removal efficiency through process optimization.

Main Methods:

• Cultivation of microalgae using second lagoon wastewater.
• Manipulation of carbon sources (bicarbonate vs. 2% CO2 gas).
• Adjustment of nitrogen to phosphorus (N:P) ratios and hydraulic retention time (HRT).

Main Results:

• Longer HRT increased algal species diversity and lipid content but decreased biomass productivity.
• Carbon sources influenced species composition: bicarbonate favored diatoms at higher pH, while CO2 favored filamentous green algae at lower pH, reducing biomass.
• Optimal phosphate addition (0.5 mg/l P) maximized chlorophyll-a and lipid productivity, indicating phosphorus limitation.
• Balanced N:P ratios enhanced nitrogen and phosphorus removal efficiencies.

Conclusions:

• Optimizing the N:P ratio is critical for maximizing algal growth, lipid productivity, and nutrient removal efficiency.
• Hydraulic retention time (HRT) and carbon source selection significantly impact microalgal community structure and productivity.
• Wastewater-based microalgal cultivation presents a promising strategy for sustainable biodiesel production and effective wastewater treatment.