Application oriented bioaugmentation processes: Mechanism, performance improvement and scale-up

[Display omitted] •Bioaugmentation mechanism based on microbial community structure are analyzed.•Operation regulation and immobilization are proposed to overcome possible failures.•Feasible approaches for the scale-up application of bioaugmentation are summarized.•Research gaps and future challenges from micro to macro level are proposed. Bioaugmentation is an optimization method with great potential to improve the treatment effect by introducing specific strains into the biological treatment system. In this study, a comprehensive review of the mechanism of bioaugmentation from the aspect of microbial community structure, the optimization methods facilitating application as well as feasible approaches of scale-up application has been provided. The different contribution of indigenous and exogenous strains was critically analyzed, the relationship between microbial community variation and system performance was clarified. Operation regulation and immobilization technologies are effective methods to deal with the possible failure of bioaugmentation. The gradual expansion from lab-scale, pilot scale to full-scale, the transformation and upgrading of wastewater treatment plants through the combination of direct dosing and biofilm, and the application of side-stream reactors are feasible ways to realize the full-scale application. The future challenges and prospects in this field were also proposed.