Rapid Start-up Of The Anammox Process By Denitrifying Granular Sludge And The Mechanism Of The Anammox Electron Transport Chain

Anaerobic ammonium oxidation?anammox?process has become a promising technology.Compared with conventional biological nitrogen removal processes,the anammox process has many advantages,such as no demand for oxygen and organic carbon,surplus sludge production and less CO₂ or N2 O emissions.However,the anammox start-up time was too long due to the long doubling time?7-14d?,and the anammox reactor was easy to instability due to the anammox was sensitive to external environment.In this study,the anammox process was successfully started-up by using the mixed denitrifying granular sludge-anammox bacteria seed strategy.And the anammox activity was enhanced with the influent substrate concentration increasing.The effects of temperature and pH on anammox activity were investigated.The characteristic of anammox granular sludge was investigated using SS,VSS,particle size distribution,mechanical strength and zeta as indicators.The mechanism of anammox electron transport chain was studied by different inhibitors.Moreover,the anammox bacteria “ growth factor” was found in this study,which could increase the anammox activity.This finding paved the way for rapid start-up anammox process.The major conclusions were as follows:1)Two UASB reactors?R1 and R2?were rapidly and successfully started-up on days25 and 28,respectively,with nitrogen removal rates?NRRs?of 0.70 kg/?m³·d?and 0.72kg/?m³·d?at denitrifying granular sludge-anammox biomass ratios of 10:1?R1?and 50:1?R2?.The anammox bacteria optimal pH and temperature was 7 and 40?,respectively.2)The sludge physical and biological characteristic was changed in the anammox granulation process.SS and VSS of two reactors were increased,which indicated the biomass of anammox was increased.The particle size and mechanical strength anammox granular sludge was increased gradually.The amount of EPS and PN/PS was increased,which indicated that the granular sludge was aggregating.The SEM experiment showed that the filamentous denitrifying bacteria changed to spherical anammox bacteria.The anammox bacteria was dominent in reactor.3)The mechanism of the anammox electron transport chain was investigated by using different inhibitors.The results demonstrated that complex ?,complex ?,complex ? and complex ? took participate in the electron transport process.4)The “growth factor” which could enhance the anammox activity was find in this study.The denitrification EPS could increase the anammox activity,and NO₂^--N,NH₄⁺-N removal rates were 1.88-and 1.53-fold higher than the control with optimal denitrification EPS volume of 10 mL.It was only the PCRB?perchlorate reducing bacteria?EPS that slightly accelerated the NO₂^--N and NH₄⁺-N removal rates,but was still lower than the removal rates with 10 mL denitrification EPS.In conclusion,the anammox reactor was successfully and rapidly started-up by using the denitrifying granular sludge-anammox bacteria seed strategy.Denitrification EPS increased the anammox activity,which proved the seed strategy superiority and paved the way for anammox rapidly start-up.During the anammox reactor start-up period,the filamentous denitrifying bacteria changed to spherical anammox bacteria.The anammox bacteria was dominent in reactor.The mechanism of the anammox electron transport chain was investigated by inhibitor experiment.