Enhanced Tolerance and Growth of Chlorella vulgaris and Scenedesmus quadricauda in Anaerobic Digestate Food Waste Effluent.

Anaerobic digestate food waste effluent (ADFE) contains high nutrient loads and causes water pollution and waste of resources if discharged without treatment. Microalgae provides a promising strategy for nutrients recovery, biomass production, and CO₂ capture. However, due to the characteristics of high ammonia nitrogen and low C/N ratio, it is hard for the original algae to remove N and P in ADFE. Hence, this study investigated the gradient domestication of C. vulgaris and S. quadricauda to enhance their tolerance to high concentrations of ADFE and evaluated their growth and metabolic responses under ADFE concentrations ranging from 20 to 60%. The results revealed that S. quadricauda exhibited better tolerance and growth performance compared to C. vulgaris, with a 42.31% biomass increase in the 40% BG11-diluted ADFE group after domestication. Additionally, extracellular polymeric substances (EPS) secretion increased by 27.66% to help shield algal cells from pollutants. The final removal efficiencies of total nitrogen, total phosphorus, and soluble chemical oxygen demand by S. quadricauda in BG11 dilution group were 37.13%, 40.64%, and 75.45%, respectively, which indicated that domestication alleviated oxidative stress to algal cells. This work demonstrates the simultaneous ADFE treatment and cost-effective microalgal biomass production, providing new insights into microalgal cultivation for the efficient treatment and valorization of nutrient-rich ADFE for sustainability.