Effective Partial Nitrification Of Ammonia Rich Wastewater By Fluidized Bed Bioreactor

Fluidized bed bioreactor?FBBR?has been applied for wastewater treatment field for decades.Both laboratory and pilotscale studies demonstrated the high efficiency and stability of FBBR.Partial nitrification is the reaction to convert ammonia to nitrite,which could be achieved by enriching the growth of ammoniaoxidizing bacteria?AOB?and inhibiting the growth of nitriteoxidizing bacteria?NOB?.Despite the distinguished advantages of these two technologies,few studies were conducted on the application of fluidized bed bioreactor to partial nitrification.This study investigated the AOB enrichment method and the application of partial nitrification fluidized bed bioreactor on treating high ammonia wastewater.This experiment run 188 days,which included the AOB enrichment period of 30 days and continuous running period of 158 days.During the AOB enrichment period,sequencing batch reactor was employed as the reactor to cultivate the enriched AOB sludge,the operational condition was dissolved oxygen and pH maintained as 1.5 mg/L and 8.0,after running 30 days,the ammonia oxidization efficiency of the activated sludge was 68.1%,which could be inoculated into the fluidized bed bioreactor.Continuous running period included 5 phases,the system was run at different inflow rates?22.5 L/day and 30 L/day?and different inflow ammonia concentrations?100 mg N/L,200 mg N/L,300 mg N/L and 400 mg N/L?to investigate the maximum ammonia loading.Under ammonia loading of 4.8 kg N/?m³·day?,partial nitrification still could be processed in the fluidized bed bioreactor.The inflow was 30 L/day,inflow ammonia concentration was 400 mg N/L,pH was 8.0,temperature was 35?and DO was 1.3 mg/L.When the ammonia loading was 3.6 kg N/?m³·day?,the ammonia oxidization efficiency and the effluent nitrite ratio were 57.8%and 53.9%,the ammonia removal rate reached its highest level2.16 kg N/?m³·day?and the effluent NO₂N/NH₄N was 1.27,the effluent of this phase could directly be used as the inflow of anaerobic ammonium oxidation?ANAMMOX?reaction without adding extra carbon.NOBs'activity was inhibited and effluent nitrate concentration was lower than 15 mg N/L during all the phases.Free ammonia was the main factor that affect the partial nitrification.In the system,the ammonia oxidization efficiency reached the maximum value of 63%when free ammonia concentration was 12.5 mg N/L,but decreased as the free ammonia concentration increased further.While the nitrite oxidation efficiency was very low,around 9%.