Magnetic biochar-cored halophilic aerobic granules: Novel strategy for rapid formation and structural stability...

Halophilic aerobic granular sludge (HAGS) effectively treats hypersaline wastewater, offering advantages of structural compactness, microbial diversity, long functional bacteria retention, and high shock tolerance. However, long start-up times and granule disintegration limit its application. This study evaluated biochar and magnetic biochar (MBC) as carriers to accelerate formation and enhance stability. MBC reduced start-up time by providing microbial attachment sites and resolved operational instability. MBC-cored HAGS exhibited higher microbial metabolic activity, increased extracellular polymeric substance secretion (critical for stability), and enhanced microbial diversity during stable operation. Crucially, MBC's Fe₃O₄ loading inhibited filamentous fungal overgrowth, reducing abundance from 2 × 10¹⁰ (without material) to 3 × 10⁸ copies/g dry sludge. Thus, MBC proves to be a key optimization strategy for HAGS, enabling reliable application in hypersaline wastewater treatment by accelerating granule formation and ensuring long-term stability through Fe₃O₄-mediated inhibition of fungal overgrowth.