Deciphering the Changes of Sludge Toxicity and the Succession of Dominant Bacteria During the Process of Catechol Degradation by Acclimated Sludge

This study simulated catechol concentration of coal chemical wastewater to acclimate activated sludge. The degradation performance of catechol, the variation of organic toxicity and bacterial community structure in sludge during acclimation were investigated. The results showed that the ability of sludge to degrade COD and catechol was increased through the acclimation process. With the deepening of acclimation, the sludge organic toxicity was 54.3 ± 2.0%, 82.4 ± 3.0% and 91.6 ± 3.3% in blank group, mid-acclimation stage (catechol concentration was 50 mg/L) and end-acclimation stage (catechol concentration was 100 mg/L), respectively, and the organic matter with molecular weight of 5 K to 10 kDa was the main contributor to sludge toxicity. Moreover, metagenomic analysis revealed that the original bacterial expressed stress responses under the catechol toxicity inhibition at mid-acclimation stage. As the adjustment of enzyme system caused by the stress responses, the functional degradation enzymes gradually formed and the functional genes were enriched at end-acclimation stage, which were shown to be the emergence of dominant bacterial groups ( Azoarcus , Thauera , Dechloromonas ). The enzyme content and the abundance of dominant bacterial groups at end-acclimation stage increased by 20.6% and 45.0%, respectively, which enhanced the degradation performance of high concentration catechol and secondary metabolites of sludge. Graphical Abstract