Feasibility of coagulation-biological treatment of toxic herbal wastewater: Process performance, alkaloid removal and microbial characterization

Coagulation, anaerobic Expanded Granular Sludge Bed (EGSB) and Sequencing Batch Reactor (SBR), which are widely used in wastewater treatment, have important position in conventional wastewater treatment. However, these conventional processes have rarely been applied in special wastewater treatment such as toxic herbal wastewater. Can these conventional treatment processes be applied to the treatment of special wastewaters? In this study, coagulation-EGSB-SBR was used to treat a toxic herbal wastewater, and the change of microbial communities and the toxicity reduction in the process were analyzed. Under the optimal parameters, the removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), and suspended substance (SS) by the combined process were 81.26 ± 1.60 %, 96.24 ± 0.76 %, and 97.13 ± 1.26 %. The removal of aconitine, hypaconitine, mesaconitine, and benzoylmesaconine were 80.94 ± 26.96 %, 100.00 ± 0.00 %, and 89.12 ± 0.89 %. During the domestication of sludge, the microorganisms inside the SBR gradually changed from Flavobacterium to Propioniciclava and Niabella, which degraded some refractory organics. In the EGSB, the dominant bacteria changed from Propioniciclava to Bacteroides. The results of this study demonstrated that the combined process effectively removed organic pollutants and alkaloids from the wastewater.