Effects of hydraulic shear force and influent ammonia nitrogen loading rate on the recovery of deteriorated nitrifying granules
Three reactors inoculated with deteriorated nitrifying granules were employed to characterize the effects of hydraulic shear force and ammonia nitrogen loading rate on granular recovery.The deterioration of the nitrifying granules was further observed in the control reactor R0 with ammonia nitrogen loading rate of 1.6g/(L·d)and hydraulic shear force of 1.31cm/s.Additionally,the nitrifying granules exhibited over-secretion of extracellular polymeric substance(especially proteins),resulting in a significant biomass loss.However,due to the presence of higher residual ammonia concentrations(＞25mg/L),the nitrite accumulation efficiency in the R0was consistently above 85％with the NOB abundance lower than 0.66％.In R2 with ammonia loading rate of 1.6g/(L·d)and hydraulic shear force of 2.62cm/s,the settling properties of the nitrifying granules was improved,although the morphology of the granules resembled bars.Furthermore,the accumulation of nitrite was eliminated due to the enrichment of NOB in R2(the relative abundance of Nitrobacter was 10.47％).The nitrifying granules underwent successful regranulation in R1 with ammonia loading rate of 0.8g/(L·d)and hydraulic shear force of 1.31cm/s.Consequently,the sludge volume index(SVI5)was reduced from 55.6mL/g to 14.6mL/g,while the average granular size was reduced from 579μm to 294μm.The results of in-situ batch tests demonstrated that AOB and NOB in the nitrifying granules were stratified.In addition,high-throughput sequencing results showed that the differences in hydraulic shear force and ammonia loading rate caused the significant variations in the microbial community structure in each reactor.Therefore,it can be concluded that regulating the microbial growth rate by reducing the ammonia loading rate exerts a more pronounced positive impact on the restoration of nitrifying granules than hydraulic shear force.
万方数据
维普
