Energy and nutrients recovery from wastewater cultivated microalgae: Assessment of the impact of wastewater dilution on biogas yield

In this study, microalgae culture was integrated into wastewater treatment as tertiary treatment to recover nutrients such as nitrogen and phosphorous. Different wastewater dilutions were assessed to investigate the effect on microalgae biomass composition for further energy recovery in the form of biogas: photobioreactor (PBR)1: control; PBR2: 10% wastewater; PBR3 50% wastewater and PBR4: 100% wastewater. After 10 days of cultivation, PBR3 presented the highest biomass productivity, which was 47.37% higher than the control. All PBRs containing wastewater presented a 100% removal of phosphorous and up to 97.85% removal of ammonia nitrogen. Each microalgae biomass was harvested and dried for further biogas production, although no significant difference was observed, PBR4 presented a higher biogas accumulated production of 204.47 mL. These results suggest that it is suitable to integrate microalgae culture as a wastewater tertiary treatment as nutrients can be recovered in the form of biogas.

Automated summary

This study integrated microalgae culture into wastewater treatment as tertiary treatment to recover nutrients for energy recovery in the form of biogas. Different wastewater dilutions were assessed, with PBR3 containing 50% wastewater showing the highest biomass productivity. The results demonstrate the feasibility of using microalgae culture for nutrient recovery in wastewater treatment.