Optimizing <i>Scenedesmus obliquus</i> Cultivation for Enhanced Nutrient Recovery from Human Urine in a Circular Economy Framework

Abstract

Microalgae cultivation utilizing urine can extract valuable nutrients from the urine while also producing beneficial by-products. Phosphorus (P) and nitrogen (N) are nutrients vital to all living organisms. When wastewater rich in these elements is dumped into surface waterways, it leads to eutrophication. Urine contributes the bulk of the nutrients found in residential wastewater, including 10%–20% of the potassium (K), 30%–50% of the P, and 60%–80% of the N. Urine is thought to be far more effective and energy-efficient at recovering nutrients when separated from other household wastewater streams than when huge amounts of highly diluted domestic wastewater are treated. The purpose of this study was to produce microalgae using human urine as a source of nutrients. Because of the high N:P ratio of microalgal biomass, it was projected that all of the P and a significant portion of the N could be used from human urine for algal biomass growth. From this study, it was found that when Scenedesmus obliquus was grown in undiluted human urine, its specific growth rate was 0.99/day, and its ammonium and phosphate consumption were 70.10% and 75.58%, respectively. The effects of urine dilution rate on ammonium and phosphate recovery were also studied in real human urine and synthetic urine.