Salinity stress and recovery of the algal-bacterial granular sludge (ABGS) system under the influence of different N-acyl-homoserine lactones (AHLs)

The algal-bacterial granular sludge (ABGS) system was established to explore the effect of 1% salinity conditions, determine the recovery process following salinity disturbance, and probe the impacts of two N-acyl-homoserine lactones (AHLs) on the system. Exposure to 1% salinity led to the reduction of filaments and an increase in TB-EPS contents within the ABGS system. The phosphorus removal performance of the ABGS system severely decreased at 1% salinity did not restore fully during the subsequent recovery stage, demonstrating that salinity stress induced long-term inhibition. Oligotrophic bacteria were found to be enriched at 1% salinity, indicating the self-adaptation of the ABGS system against salinity stress. The addition of AHLs helped mitigate the inhibitory effect of salinity stress. Specifically, C6-HSL slowed down the decline in microbial diversity, while 3-oxo-C12-HSL weakened the inhibition on microalgae growth. This study provided novel insights into the effects of salinity stress and AHLs on ABGS systems.