Enhancing hydrolysis acidification process for coal gasification wastewater treatment through micro-aeration strategy: The role of micro-oxygen environment

Micro-aeration has been regarded as an efficient, economical, and promising strategy for enhancing the anaerobic hydrolysis acidification (HA) of toxic and recalcitrant organics. However, the available information on both its application in actual refractory industrial wastewater and the molecular-level interrelated mechanisms of functional genes and functional enzymes in pollutants degradation is limited. Herein, micro-aeration HA was exploited to investigate the degradation performance of actual coal gasification wastewater under various dissolved oxygen (DO) concentrations. In contrast, the optimal removal efficiencies of chemical oxygen demand, NH₃N, total organic carbon, and total phenols reached 53.3 %, 14.63 %, 56.5 % and 48.1 %, respectively, as well as biodegradability and detoxification capacity at 0.2–0.3 mg/L of DO. Especially, the micro-oxygen environment demonstrated a proclivity for the removal of phenolic compounds. And the activities of functional enzymes associated with phenolic degradation (phenol hydroxylase, catechol 1,2-dioxygenase and dehydrogenase) were increased. Besides, organics hydrolysis-related, toxic and recalcitrant organics degradation-related, ring cleavage enzyme-related and facultative species under 0.2–0.3 mg/L of DO were more abundant than that in reactor without DO. Finally, this micro-oxygen condition also improved the abundance of genes expressing functional enzymes involved in the metabolic processes of phenolic biochemical degradation (e.g., phenol/toluene 2-monooxygenase, catechol 1,2-dioxygenase, muconate cycloisomerase). This study provides a theoretical basis for the industrial application of micro-aeration strategy for the detoxification pretreatment of refractory industrial wastewater.