Effects of organic carbon loading on microalgal growth and community dynamics in photobioreactors

Abstract

This study investigates the impact of varying organic carbon loads on the growth, composition, and productivity of microalgae in controlled photobioreactor systems. Three laboratory-scale bioreactors were operated with synthetic wastewater containing different concentrations of Carbon (100, 400, and 800 mgL-1), while maintaining consistent nitrogen and phosphorus inputs. Parameters monitored included pH, chlorophyll a, total suspended solids (TSS), volatile suspended solids (VSS), and microalgal community composition. Microscopic analysis revealed that moderate glucose concentrations (100–400 mgL-1) favored the proliferation of Scenedesmus sp and Chlorella sp, while excessive organic carbon input (800 mgL-1) led to a decline in species diversity and overall algal biomass. Statistical analysis confirmed significant variations in pH, chlorophyll a, TSS, and VSS across treatments, with bioreactor A showing the highest values of algal productivity and pH due to optimal photosynthetic activity. The results demonstrate that moderate organic carbon enrichment enhances algal growth and trophic complexity, while excessive organiccarbon suppresses phytoplankton development, likely due to microbial competition and acidification. These findings provide valuable insights for optimizing organic carbon inputs in algal-based wastewater treatment and ecological restoration strategies.