Microbial interactions as a function of operational variables in microalgal-based wastewater treatment

Microalgae-based wastewater treatment is a promising biotreatment technology that offers advantages such as high efficiency in nutrient recovery, robustness, and the production of valuable biomass. In recent decades, numerous studies have focused on optimizing these processes to reduce costs and enhance nutrient uptake and biomass productivity. However, changes in the operational variables of large-scale reactors not only affect biomass productivity but also influence the growth of coexisting microorganisms, such as bacteria, and the presence of contaminants like pathogens and fungi. This study presents a comprehensive microbial characterization of a microalgae culture produced in a pilot-scale raceway reactor of 80m2, fed with untreated urban wastewater. During the study, control strategies for pH, dissolved oxygen, and culture height were altered to evaluate changes in the microbial population based on operational conditions. Special attention was given to the microalgal strain produced, as well as the bacteria populations (including nitrifying bacteria, pathogenic bacteria, and photosynthetic bacteria), and fungi present in the culture under each set of conditions.