Effect of light intensity on the operational performance of algal-bacterial granular sludge system

This study investigated the effects of light intensity (3000, 6500, and 10000 lux) on the pollutant removal performance and biomass dynamics of algal-bacterial granular sludge (ABGS). Results showed that although ammonia nitrogen removal reached 100% at all intensities, 6500 lux was the optimal condition, achieving the highest average removal efficiency for total nitrogen (52.22%), chemical oxygen demand (95.16%), and phosphate (52.67%). Under 3000 lux, high dissolved oxygen levels inhibited the competitive ability of denitrifying bacteria, resulting in a total nitrogen removal efficiency of only 29.63%. In contrast, 10000 lux caused significant photoinhibition and damaged PSII reaction centers, with chlorophyll concentration dropping by 54.29% compared to the 6500 lux group. Excessive light energy also induced oxidative stress and nutrient depletion, leading to decreased biomass concentrations and microbial growth rates. In conclusion, 6500 lux light intensity promotes synergistic interactions between algae and bacteria, ensuring stable biomass accumulation and superior decontamination performance, providing critical technical parameters for the engineering application of ABGS systems.