Effects of light intensity and salinity on formation and performance of microalgal-bacterial granular sludge

Photosynthetic microorganisms in microalgal-bacterial granular sludge offer advantages in wastewater treatment processes. This study examined the effects of light intensity and salinity on microalgal-bacterial granular sludge formation and microbial changes. Activated sludge was inoculated into three bioreactors and operated in batch treatment mode for 100 days under different light intensities (0, 60, and 120 μmol m−2 s−1) and staged increases in salinity concentration (0, 1, 2, and 3%). Results showed that microalgal-bacterial granular sludge was successfully formed within 30 days, and high light exposure increased algal particle stability and inorganic nitrogen removal (63, 66, 71%), while chemical oxygen demand removal (>95%) was similar across groups. High-throughput sequencing results showed that the critical algae were Chlorella and diatoms, while the main bacteria included Paracoccus and Xanthomarina with high extracellular polymeric substance production. This study aims to enhance the comprehension of MBGS processes in saline wastewater treatment under varying light intensities.