Enhanced microalgae cultivation using wastewater nutrients extracted by a microbial electrochemical system

Area of Science:

• Environmental Biotechnology
• Wastewater Treatment
• Algal Cultivation
• Circular Economy

Background:

• Directly cultivating algae in wastewater faces challenges like bacterial contamination and low biomass density.
• Resource recovery from wastewater is crucial for a circular economy.
• Microalgal cultivation offers potential for nutrient removal and biomass production.

Purpose of the Study:

• To investigate microalgal cultivation in a photobioreactor (PBR) using nutrients extracted from wastewater by a microbial nutrient recovery cell (MNRC).
• To address challenges of bacterial contamination and low biomass density in direct wastewater-based algal cultivation.
• To evaluate the efficiency of nutrient recovery and microalgal growth enhancement.

Main Methods:

• A microbial nutrient recovery cell (MNRC) was used to extract nutrients from wastewater.
• The extracted nutrients were used to feed a photobioreactor (PBR) for microalgal cultivation.
• System performance was evaluated based on chemical oxygen demand (COD) removal, nutrient recovery rates (NH4+-N, PO43--P), and microalgal biomass density and lipid content.

Main Results:

• The MNRC-PBR system achieved 96% COD removal and recovered 44% NH4+-N and 39% PO43--P.
• Microalgae cultivated in the MNRC-derived medium showed an 8.3-fold increase in biomass density and 1.4-fold higher lipid content compared to direct wastewater cultivation.
• Biomass purity reached 90% microalgae in the MNRC-PBR system, significantly higher than the ~30% in raw wastewater.

Conclusions:

• The MNRC-PBR system effectively extracts nutrients from wastewater, enhancing microalgal growth and biomass quality.
• This approach offers a viable strategy for resource recovery from wastewater, contributing to a circular economy.
• Further optimization is needed to manage challenges like accumulated salinity during extended operation.