Comprehensive Analysis of the Regulatory Effect of Fe 3 O 4  On Aerobic Granular Sludge in Response to High Salt and Fluctuating C/N Stress in Seafood Processing Wastewater

Abstract

To address the poor performance of aerobic granular sludge (AGS) in the treatment of seafood processing wastewater with high salinity and fluctuating C/N ratio, this study explored an exogenous Fe3O4 dosing strategy to stimulate the stress response. The results showed that 1.5 g/L Fe3O4 stimulated the secretion of more hydrophobic aromatic proteins and viscous polysaccharides in AGS at a salinity of 35 gNaCl/L and the C/N ratio increased from 10 to 20 and then decreased to 10 and 5, effectively inhibiting the shedding of bacterial consortia from granules. The improved electron transport efficiency guaranteed a high metabolic rate for microorganisms. Meanwhile, the enrichment of Glutamicibacter and Ferruginibacter played an important role in response to high salt and fluctuating C/N stresses. Fe3O4 was found to upregulate the expression of functional genes associated with nitrogen conversion. This study provided new insights to improve the robustness of AGS in seafood processing wastewater treatment.

Keywords: Granular sludge, Fe3O4, high-salt, fluctuating C/N ratio, electron transfer.