Straw foam-based aerobic granular sludge (SF-AGS) for high-salinity wastewater treatment: performance, microbial...

Saline wastewater can cause severe damage to the natural environment, yet its physicochemical treatment methods are generally energy-intensive and costly. In this study, a novel straw foam-based aerobic granular sludge (SF-AGS) was employed to protect microbial communities from salinity stress under three experimental conditions: no salinity (R1), salinity with NaCl (R2), and salinity with NaCl + Na₂SO₄ (R3). Results indicated that mature SF-AGS maintained excellent settling performance and high biomass concentration even at 4.0% salinity. The SF-AGS exhibited high removal efficiencies for COD, NH₄⁺-N, TP and TN in both pure-salt and mixed-salt reactors, achieving approximately 91%, 80%, 30% and 75%, respectively, highlighting its high tolerance to high-salinity conditions without significant deterioration in overall performance. Gradual salinity increases substantially altered the microbial community composition, with halotolerant taxa such as Raineyella and Sphingopyxis becoming more abundant and salinity-driven shifts in nitrification processes indirectly affecting phosphorus removal under high-salinity conditions. These findings demonstrate SF-AGS exhibits robust salinity tolerance and its promising applicability for high-salinity wastewater treatment.