Regulating mechanism of denitrifier Comamonas sp. YSF15 in response to carbon deficiency: Based on carbon/nitrogen functions and bioaggregation

Novel flocking materials as biocarriers in moving bed biofilm reactor for improving simultaneous nitrification and denitrification performance

Biocarrier is the key factor for the stable operation of moving bed biofilm reactor (MBBR). To achieve efficient simultaneous nitrification and denitrification (SND), this study provided novel flocking materials as biocarriers. The biofilm formation experiment showed that longer flocking carrier was more conducive to biomass accumulation, resulting in greater oxygen uptake rate. The continuous operation results showed that the total nitrogen removal and SND performance of the MBBR with the addition of 5.0 mm flocking carriers reached 52.0 % and 70.5 %, respectively, which were 29.1 % and 33.3 % greater than those of the control. Compared with those in suspended sludge, the extracellular polymeric substances and protein components in the biocarrier were more abundant. Furthermore, the relative abundance of genera related to denitrification and the nitrogen metabolic sequence improved with the addition of the novel flocking biocarriers. This study demonstrated the effectiveness of novel flocking fillers in improving the performance of MBBR.

Development of partial denitrification process in upflow-anaerobic sludge blanket and effect of electric field on partial denitrification performance

Partial denitrification (PD) is an alternative to providing NO2- for the anaerobic ammonium oxidation (anammox) process. In this study, three upflow anaerobic sludge blankets (UASB) were used to investigate the effect of an external electric field on PD performance. The results indicated that the maximum nitrite transformation ratio (NTR) reached 76.3 %, with an average NTR of 54.1 %, in the presence of external electric field, whereas the average NTR of the control was only 49.8 %. The fitted maximum specific nitrate reduction rates of PD1, PD2, and PD3 were 83.7, 90.5, and 92.3 mg N g-1VSS h-1, respectively, according to the Haldane model analysis. Microbial community analysis demonstrated that the abundance of Thauera, Comamonas, and Accumulibacter increased with electric assistance. In summary, UASB reactor with electrodes set in the upper region was most feasible for the stable PD process, providing an alternative for developing a coupled PD-anammox process.