Study On Culture And Short-cut Nitrification Of Aerobic Granular Sludge

Granular sludge has become a research hotspot because of its advantages of Anti-toxic,high hydraulic load,structural stability,the variety and quantity of microorganisms,and the good performance of removal of pollutants.However,the current research on granular sludge mostly focuses on the cultivation of aerobic granular sludge by artificial allocated water due to longer culture period and low stability during storage.Therefore the granular sludge technology can not be applied in actual sewage treatment.This paper mainly studies the formation of granular sludge using domestic sewage,the optimization of short-cut nitrification,and the activity recovery of disintegrated granular sludge in order to aim to provide technical reference for its engineering application.The main research contents are as follows.?1?Stage of cultivating granular sludgeTo explore the effect of water quality changes on the culture period of granular sludge,the SBR reactors of R1 and R2 with the same specifications were adopted.The temperature was controlled at 25°C,and the sludge was inoculated from the secondary sedimentation tank of the sewage treatment plant,which has a sedimentation rate of 19.1m/h.The influent NH₄⁺-N and COD concentrations were 65.00 and 220.00 mg/L,respectively,and then the powdered activated carbon was added to the influent.R1 is fed by artificial allocated water in the cycles of 1³5,and by domestic sewage in cycles of 36¹24.R2 is fed by artificial allocated water in the initial stage,and then domestic sewage was added gradually,and finally100%of domestic sewage was used in the 30th cycle.In order to culture granular sludge the precipitation time was shortened gradually.In the 88th cycle of the R1 reactor the effluent NH₄⁺-N,NO₂^--N,NO₃^--N and COD concentrations were stabilized in 0.67,0.63,17.81 and38.25 mg/L,respectively.Extracellular polymeric substances including the protein?PN?and polysaccharide?PS?were 286.56 and 67.98 mg/L,respectively,and the particle size Granular sludge formed was mainly concentrated at 1.5-2.0 mm,and its sedimentation rate was 60.3m/h.In the 72th cycle of the R2 reactor,the effluent NH₄⁺-N,NO₂^--N,NO₃^--N and COD concentrations were 0.98,0.83,17.59 and 38.45 mg/L,respectively,the PN and PS were278.56 and 68.26 mg/L,respectively.Its the particle size was mainly concentrated at 1.5-2.0mm too,and the sedimentation rate was 60.4 m/h.Therefore,the influent change of wastewater quality of the R2 reactor is more helpful to the form granular sludge.To investigate the effect of powdered activated carbon and low temperature conditions on the formation of granular sludge.The SBR reactors R1,and R3 and R4 with the same size as R1were used.R1 was fed by wastewater added with activated carbon,R3 influent was not added with activated carbon,and other operating conditions were consistent.The operating temperatures of R3 and R4 were 25°C and 15°C,respectively.In the 32nd cycle of the R1reactor,the effluent NH₄⁺-N,NO₂^--N,NO₃^--N and COD concentrations were 0.69,5.47,5.99and 31.80 mg/L,respectively,PN and PS were 225.26 mg/L and 60.25 mg/L,respectively,and the sedimentation rate was 58.2 m/h.In the 38th cycle of the R3 reactor,the effluent NH₄⁺-N,NO₂^--N,NO₃^--N and COD concentrations were 0.69,3.56,9.25 and 31.60 mg/L,respectively,PN and PS were 258.56 and 60.26 mg/L,respectively,and the sedimentation rate was 56.3 m/h.The effluent NH₄⁺-N,NO₂^--N,NO₃^--N and COD concentrations in the R4reactor at the 58th cycle were 4.83,0.71,17.59 and 45.16mg/L,respectively,the PN and PS were 182.26 and 58.16 mg/L,respectively,and the sedimentation rate was 50.5 m/h.Compared with R3,the granular sludge formed in the R1 reactor with activated carbon has a higher sedimentation rate.Compared with R4,the granular sludge formed in R3 under normal temperature conditions has better pollutant removal ability and sedimentation performance.?2?Aeration rate on short-cut nitrification granular sludge cultivationTo exploring the effect of aeration on short-cut nitrification of granular sludge.The mature aerobic granular sludge was used as the seed,and three SBR reactors with the same specifications were used.The sedimentation time was 5 min,and the controlled aeration rates were 70,100,130 L/h,and the influent NH₄⁺-N and COD concentrations were 65.00 and220.00 mg/L,respectively.When the aeration rate was 70L/h,the NH₄⁺-N,NO₂^--N and COD concentrations in the 50th cycle were 0.98,17.32 and 37.56mg/L,respectively,and the NO₂^--N accumulation rate was 89.4%,the specific ammonia oxidation rate?SAOR?was 0.46g·?g·d?^-1.When the aeration rate was 100L/h,the NH₄⁺-N,NO₂^--N and COD concentrations in the 41st cycle were 0.98mg/L,20.05mg/L and 32.16mg/L,respectively,and the NO₂^--N accumulation rate was 93.5%,and the SAOR was 0.47g·?g·d?^-1.When the aeration rate was130L/h,the NH₄⁺-N,NO₂^--N and COD concentrations in the 32nd cycle were 1.05,20.56 and32.26mg/L,respectively,and the NO₂^--N accumulation rate was 92.4%,and the SAOR is0.48g·?g·d?^-1.Short-cut nitrification was achieved in the three aeration rates,but the optimized aeration rate was 100 L/h.?3?Effect of salinity on short-cut nitrification granular sludgeTo investigate the effect of salinity on short-cut nitrification of granular sludge,the aeration rate of SBR reactor was control at 100 L/h,the sedimentation time was 5 min,and the influent NH₄⁺-N and COD concentrations were 65.00 and 220.00 mg/L,respectively.NaCl was added to the influent and the salinity were 0.6%,1.0%,3.0%,5.0%and 7.0%.When the salinity was 0.6%,the effluent NO₂^--N is 17.38 mg/L,the NO₂^--N accumulation rate was90.5%,and the PN and PS were 290.16 and 70.26 mg/L,respectively.When the salinity was1.0%,the effluent NO₂^--N was 20.16 mg/L,the NO₂^--N accumulation rate was 92.7%,and the PN and PS were 32.56 mg/L and 71.26 mg/L.When the salinity was 3.0%,the effluent NO₂^--N was 23.89 mg/L,the NO₂^--N accumulation rate was 92.8%,and the PN and PS were315.26 and 70.26 mg/L.When the salinity was 5.0%,the effluent NO₂^--N was 25.16 mg/L,the NO₂^--N accumulation rate was 94.8%,and the PN and PS were 295.26 and 69.26 mg/L.When the salinity was 7.0%,the effluent NO₂^--N was 16.54 mg/L,the NO₂^--N accumulation rate was 89.8%,and the PN and PS were 191.26 and 69.65 mg/L.When the salinity is 5.0%,the short-cut nitrification performance is the best.?4?Strengthening recovery of granular sludge after disintegrationThe strengthening recovery of the granular sludge after the disintegration was investigated.The mature granular sludge by high hydraulic shear force was disintegrated,and then strengthening recovery was implemented.Using the SBR reactor,the influent NH₄⁺-N and COD concentrations were 65.00 and 220.00 mg/L,respectively,and the precipitation time was 5 min.During the recovery period,the effluent NH₄⁺-N,NO₂^--N,NO₃^--N and COD concentrations were 0.61,16.97,0.99 and 32.16 mg/L,SAOR and SNiPR were 0.28 g·?g·d?^-1and 0.08 g·?g·d?^-1,respectively.The particle size of the recovered granular sludge is mainly concentrated between 2.0 and 2.5 mm,that is,the newly formed granular sludge has a larger particle size than primory aerobic granular sludge.During the recovery period,the sedimentation rate of granular sludge increased from 38.2 to 63.1m/h,and the particle size increased from 0.5 to 2.5mm.The recovery of granular sludge after disintegration was successfully achieved.