Review of micro-aeration hydrolysis acidification for the pretreatment of toxic and refractory organic wastewater

Micro-aeration (dosing tract air or oxygen) is an effective method to promote hydrolysis acidification (HA). In recent years, the pretreatment of toxic and refractory organic wastewater has attracted increasing attention. As micro-aeration in the HA process accelerates hydrolysis, improves volatile fatty acid production, increases biodegradability, scavenges hydrogen sulfide, promotes enzyme activity, and facilitates the diversity of functional microbes, this review evaluated the underlying mechanisms for each of these processes. Furthermore, by summarizing the process parameters and control strategies, the factors involved in the implementation of the micro-aeration HA process were revealed. In addition, we summarized previous applications of various toxic and refractory organic wastewater pretreatments to provide guidance for potential large-scale implementation. Finally, the challenges and future perspectives of using micro-aeration HA to pretreat toxic and refractory organic wastewater were highlighted. Further scope of the study includes removal mechanisms of toxic and refractory organic matter, the development of automatic processes with intrinsic control and long-term stability, development of new antifouling and economical microaerobic membrane materials, CFD simulations for the evaluation of micro-aeration transfer of different aeration methods, and mathematical modeling describing micro-aeration effects in HA. [Display omitted] •Micro-aeration in HA facilitates processing efficiency and system stability.•Micro-aeration leads to a high yield of functional microbes and excreted enzymes.•Factors influencing the micro-aeration HA process control are summarized.•Micro-aeration HA has been successfully applied to the pretreatment of various wastewaters.