Impact of indigenous vs. cultivated microalgae strains on biomass accumulation, microbial community composition, and nutrient removal in algae-based dairy wastewater treatment

This study investigated the role of indigenous and cultivated microalgae in nutrient removal and biomass production in dairy wastewater, especially in microbial function change. Five indigenous and three cultured microalgal strains were grown in sterile and non-sterile dairy wastewater, and nutrient removal and biomass profiles were analysed. Results showed higher phosphorus removal (90.1 % vs. 81.8 %, p < 0.001) and biomass production (2.3 vs. 2.0 g/L, p < 0.001) in sterile wastewater, while nitrogen removal was higher in non-sterile wastewater (83.1 % vs. 77.5 %, p < 0.05). Indigenous strains grew more consistently in high-concentration wastewater, though not significantly different from cultured strains. Phycosphere bacteria communities were more closely associated with total nitrogen, total phosphorus, and pigment content, while free-living bacteria primarily dependent on chlorophyll a and extracellular polymeric substances (EPS). The nitrogen transforming function was enhanced in phycosphere. These findings provide insights for optimizing microalgal-based wastewater treatment, advancing sustainable dairy wastewater management.