Effects Of Fe NPs And Mn NPs On The Performance And Microbial Communities Of Anammox Granules

In view of the wide application of nanomaterials and the advantages of high efficiency and low consumption of anaerobic ammonium oxidation?anammox?process,we attempted to study the effects of nanomaterials on the anammox process.The robustness of the anammox process under nanoscale Zero-Valent Iron?nZVI?shock,hydraulic shock and their combination were investigated.Then,the effects of Fe₃O₄ nanoparticles?NPs?on the performance,sludge characteristics and microbial community of the anammox process were analyzed.Finally,the effects of MnO₂ NPs on the performance,sludge characteristic and microbial community of the anammox process were explored,and the relationship between microbial community and performance were also discussed in this study.?1?The stability and resilience of an anammox system under transient nZVI(50,75 and 100 mg L^-1),hydraulic shock?2-fold increase in flow rate?and their combination were studied.The response to the shock loads can be divided into three phases i.e.shock,inertial and recovery periods.The effects of the shock loads were directly proportional to the shock intensity.The effluent quality was gradually deteriorated after exposure to 100 mg L^-1 nZVI for 2 h.Notably,the specific anammox activity?SAA?and the content of heme c were considerably reduced during the shock phase and the maximum loss rates were about 30.5%and 24.8%,respectively.Nevertheless,the extracellular polymeric substances?EPS?amount in the shock phase was enhanced in varying degrees and variation tendency was disparate at all the tested shock loads.These results suggested that robustness of the anammox system was dependent on the magnitude shocks applied and the reactor resistance can be improved by reducing hydraulic retention time with the increase of nZVI concentration under these circumstances.?2?The performance,sludge characteristic and microbial community of anammox sludge from an up-flow anaerobic sludge blanket?UASB?reactor were investigated under long-term exposure of magnetic Fe₃O₄ NPs.The nitrogen removal had no obvious variation at 1-200 mg L^-1 Fe₃O₄ NPs compared to 0 mg L^-1 Fe₃O₄ NPs.When Fe₃O₄ NPs concentration gradually increased from 1 mg L^-1 to 60 mg L^-1,SAA decreased from 287.0±13.2 mg TN g^-1VSS d^-1 to 253.0±9.2 mg TN g^-1VSS d^-1,while the SAA increased to 381.8±15.8 mg TN g^-1VSS d^-1 at 200 mg L^-1 Fe₃O₄ NPs.And the heme c content,EPS amounts and Vs in anammox granules could also be influenced by Fe₃O₄ NPs,which had similar variation trends to the SAA.High throughput sequencing showed that the long-term exposure of anammox granules to Fe₃O₄ NPs could obviously influence the microbial richness and diversity of anammox biomass with a trend of firstly decreasing and then increasing.And Candidatus Kuenenia was always the dominant species,and its abundance up to33.4%when the Fe₃O₄ NPs concentration was up to 200 mg L^-1.These results demonstrated that Fe₃O₄ NPs had an effect of pre-stress and post-acclimation on anammox granular sludge.?3?The long-term impacts of MnO₂ NPs on performance,sludge characteristic and microbial community of biogranule-based anammox process were evaluated.It was found that the total nitrogen removal efficiency of reactor was fluctuated between90%-93%at 1-200 mg L^-1 MnO₂ NPs.Notably,the SAA was increased with increase of the MnO₂ NPs concentration.The SAA was up to maximum value of 657.3±10.6mg TN g^-1VSS d^-1 at 200 mg L^-1 MnO₂ NPs,which had similar varied trends to the content of heme c and EPS in anammox granules.High throughput sequencing indicated that MnO₂ NPs could improve the microbial richness and diversity of anammox granules and Candidatus Kuenenia was always the dominant species,and its abundance continued to increase to 23.9%at the end of operational experiment.Therefore,MnO₂ NPs could be applied to enhance the anammox process and the influent MnO₂ NPs concentration was lower than 200 mg L^-1 in view of the reactor performance and cost issues.