Construction of immobilized functional microflora system and research on mechanism of enhanced degradation of aromatic compounds in coal chemical wastewater.

Aiming to address the practical challenges of aromatic compound degradation in the biochemical treatment system of coal chemical wastewater (CCW), this study constructed an immobilized functional microflora system using modified zeolite as a bacterial carrier. The study evaluated the system's continuous efficacy in degrading aromatic compounds and explored the underlying mechanisms of the immobilized microflora system in enhancing degradation. The findings demonstrated that zeolite material modified by calcination at 300 °C exhibited the highest immobilization capacity for the microflora, achieving a microorganism immobilization amount of 0.81 mg/g. Additionally, when the chemical oxygen demand (COD) concentration stabilized at 1250 ± 20 mg/L, COD removal was maintained steadily above 65 %. The removal efficiencies for phenols and polycyclic aromatic hydrocarbons were 76.85 % and 52.52 %, respectively, representing enhancements of 19.17 % and 23.15 % compared to the control group (activated sludge alone). The secretion characteristics of microbial extracellular polymeric substances and the variation in protein secondary structure and hydrogen bonding structure were further analyzed. The results indicated enhanced secretion of the protein and the polysaccharide, an increased α-helix to (β-sheet + random coil) ratio, and stronger intermolecular hydrogen bonding. These findings suggest that the immobilized microflora system improved microbial adaptability to environmental stress. Additionally, increased expression of key enzymes such as Dehydrogenase, Catechol 1,2-dioxygenase, and Catechol 2,3-dioxygenase, alongside enhanced levels of dominant bacteria like Candidatus_Competibacter, Luteococcus and Flavobacterium underscored the critical role of immobilized functional genera in the degradation of aromatic compounds. The results of the study are of great practical significance for the regulation of the operation stability of the biochemical treatment system of CCW and the realization of the completely harmless treatment of CCW.