2026 Volume 62 Issue 3 Pages 37-53
Microalgae–activated sludge (MAS) systems have attracted increasing attention as energy-efficient wastewater treatment technologies because they simultaneously enhance nutrient removal and biomass production while reducing aeration requirements. Whether these benefits are universally conserved among phylogenetically distinct microalgae or are microalgal species dependent remains unclear. In this study, three representative microalgae–Chlamydomonas reinhardtii, Chlorella vulgaris, and Euglena gracilis–were comparatively evaluated using sequencing batch MAS systems operated for 20 consecutive cycles. Wastewater treatment performance, biomass production, and bacterial community dynamics were investigated to determine the influence of each microalgal species on reactor performance. While all three MAS systems enhanced nitrogen removal compared to activated sludge alone, demonstrating the broad applicability of MAS technology, reactor performance differed markedly among these microalgal species. E. gracilis–activated sludge exhibited the highest DOC, TN, and TP removal efficiencies (83.6%, 60.1%, and 75.9%, respectively) together with the greatest biomass production rate (42.2 mg/L/d). Amplicon sequencing of bacterial 16S rRNA genes revealed that each microalgal treatment was associated with a distinct bacterial community. Notably, the persistence of nitrifying bacteria and the presence of bacterial groups potentially associated with denitrification in EG－AS coincided with stable nutrient removal throughout the experiment. These findings demonstrate that microalgal species substantially affect reactor performance and are associated with differences in bacterial community composition, highlighting microalgal species selection as a critical design parameter for optimizing MAS systems.
