Light intensity-regulated glycogen synthesis and pollutant removal in microalgal-bacterial granular sludge for wastewater treatment

Abstract

As light intensity plays a pivotal role in the microalgal-bacterial granular sludge (MBGS) process, understanding its impact on system performance and energy dynamics is essential. This study investigated the effects of varying light intensities (20, 100, 200, and 300 μ mol/m²/s) on the performance of MBGS in urban wastewater treatment, with a particular focus on glycogen accumulation and pollutant removal. The results demonstrated that light intensity significantly influenced microbial community structure, glycogen accumulation, and pollutant removal efficiency. At the lowest light intensity (20 μ mol/m²/s), filamentous Cyanobacteria dominated, leading to poor settling performance but enhancing phosphate removal due to increased polyphosphate metabolism. As light intensity increased, the microbial community shifted from Cyanobacteria to eukaryotic algae (e.g., Chlorella) at higher intensities. The optimal light condition (200 μ mol/m²/s) favored glycogen synthesis and improved synergistic interactions between microalgae and bacteria, ensuring stable pollutant removal. Notably, increased light intensity upregulated the expression of genes encoding glycogen branching enzyme (EC: 2.4.1.18), promoting glycogen accumulation in the MBGS system. These findings provide valuable insights for optimizing MBGS systems to achieve efficient urban wastewater treatment and resource recovery.

Keywords: Environmental adaptability; Glycogen accumulation; Microbial community; Synergistic interactions; Urban wastewater treatment.