Application of a Spiral Symmetric Stream Anaerobic Bioreactor for treating saline heparin sodium pharmaceutical wastewater: Reactor operating characteristics, organics degradation pathway and salt tolerance mechanism.

In this study, a Spiral Symmetry Stream Anaerobic Bioreactor (SSSAB) was adopted for treating actual saline heparin sodium pharmaceutical wastewater (HSPW). After adaptation, under the influent COD of 8731 mg/L, OLR of 6.98 kg COD/(m³•d) and salinity of 3.57 wt%, the COD removal reached up to 82%. This value is much higher than the reported for the other reactors at similar salinity. Benzenes are the major organic compounds in HSPW. The main rate-limiting steps are the degradations of phenol and p-cresol. In addition, the degradation pathways of typical benzenes in HSPW were analyzed. After adaptation, the soluble salt content in the granular sludge increased, and the bacterial extracellular polymers (EPS), especially tightly-bound EPS also significantly increased. 16S rRNA analysis revealed that the microbial community in the anaerobic granular sludge (AGS) had become adapted to the HSPW treatment since Mesotoga (12.4%), Anaerophaga (9.0%), Oceanotoga (6.1%) and Aminobacterium (4.1%) increased from previously below 1.0% values. The relative abundance of Methanosarcina in the upper layer of the reactor (68.7%) is significantly higher than that at the bottom (3.8%). This proves the superiority of the SSSAB structure. Finally, a model for salt-tolerant microorganisms is given, which proposes a mechanism for this study and provides reference for other anaerobic biological treatments of high-salt containing wastewater.