• • Capsule shell pore size (0.25 ± 0.063 μm) enables rapid mass transfer; nitrate removal reached 83.61% by day 21, demonstrating fast activity recovery critical for industrial RAS integration.
• • Biomass increased to (21.96 ± 0.28) mg·(g-pellet)−1 by day 30, while effective diffusion coefficient declined to 0.232 × 10−9 m²·s−1, indicating a trade-off between biomass accumulation and substrate transport that must be managed for sustained performance.
• • Dominant genera after acclimation: Methylobacterium (22.8%), Brevibacillus (18.1%), Azospirillum (17.3%); nirS/nirK denitrifiers >99% Proteobacteria, with increases in Bosea, Bradyrhizobium, Rhizobacter, Alicycliphilus, and Zoogloea, enhancing metabolic versatility and biofilm formation.
• • Effective diffusion coefficient stabilized at ~0.233 × 10−9 m²·s−1 from day 21–30, correlating with biomass stabilization, providing a design parameter for predicting long-term capsule performance.