Bioaugmentation of aerobic granular sludge with Gordonia sp. P6 for enhanced quinoline degradation: Synergistic...

Quinoline, a nitrogenous heterocyclic compound commonly found in coking wastewater, poses substantial environmental and health risks due to its high solubility, mobility, and carcinogenic properties. In this study, Gordonia sp. P6, an efficient quinoline-degrading strain, was applied to bioaugment aerobic granular sludge (AGS) systems, aiming to enhance quinoline degradation at elevated concentrations. The results indicated that a strain-to-sludge ratio of 1.5 % (w/w) was identified as the optimal bioaugmentation ratio. At this ratio, a quinoline degradation rate of 99.23 % was attained, and the acclimation period was shortened to less than 5 days. The bioaugmented AGS exhibited enhanced extracellular polymeric substance (EPS) secretion (increasing from 58.89 ± 2.42 mg/g MLVSS to 98.98 ± 4.36 mg/g MLVSS), along with improved granule stability and nutrient removal efficiency. Molecular ecological network analysis revealed that the addition of Gordonia sp. P6 reorganized the microbial community structure, increasing the proportion of cooperative interactions from 46.37 % to 55.48 % and strengthening network stability. Notably, the Actinobacteria subnetwork expanded in scale and connectivity, with Gordonia sp. P6 occupied 82.14 % of positive links within this phylum. Synergistic partnerships were established between Gordonia sp. P6 and functional taxa such as the nitrifying bacteria Parapusillimonas and denitrifying bacteria Thauera, Erysipelothrix, and Flavobacterium, suggesting their potential contribution to the enhanced total nitrogen (TN) removal efficiency. These findings demonstrated that bioaugmentation by highly efficient quinoline-degrading functional strains was an effective approach to alleviating quinoline toxicity, stabilizing the operation of the AGS system, and facilitating microbial cooperation. This study provided a novel strategy for the nitrogenous heterocyclic compounds wastewater.