• • AGS cultivation in SBR achieved dense granules of ~1 mm within 60 days, with EPS content of 92.22 mg·L−1, enabling COD and color removal of 88.5% and 73.3%, respectively, demonstrating effective treatment of real textile wastewater.
• • Optimal OLR of 3.0 kg·(m3·d)−1 maximized granule size (1.38 mm) and EPS content (95.21 mg·g−1), yielding the highest COD and color removals (92.73% and 86.35%), while an OLR of 5.0 kg·(m3·d)−1 caused sludge bulking and disintegration, indicating a critical operational threshold.
• • Proteobacteria (44.06%–49.17%) and Bacteroidetes (27.49%–29.64%) dominated the microbial community, with their abundances positively correlated with EPS protein secretion and pollutant degradation, highlighting key phyla for process performance.
• • OLR regulated the abundance of functional genera such as Pseudomonas and Shewanella, as well as the expression of azoR and amoA genes, forming an efficient pollutant degradation network that underpins the treatment system's robustness.