Study On Culture And Stable Operation Characteristics Of Aerobic Granular Sludge

Compared with activated sludge,the aerobic granular sludge structure is compact,with high sedimentation speed,easy to separate mud and water;high biomass,high volumetric load,strong resistance to load shock;Integrating anaerobic,aerobic and anoxic microorganisms,it can achieve the effects of simultaneous decarbonization,denitrification and dephosphorization,so aerobic granular sludge is a very promising sewage treatment technology.However,during the long-term operation,the granules are prone to filamentous bacteria swelling,easy to break,and poor in function and structure.It is the main factor limiting the industrial application of the technology,and is also one of the hotspots of current research.In this experiment,the artificial sewage was firstly simulated,and the aerobic granular sludge was cultured by the SBR reactor in the anaerobic/aerobic operation mode by shortening the settling time to increase the selection pressure,shortening the operation cycle and increasing the volume exchange rate to increase the organic load.The average granule size of the fully granulated aerobic granular sludge is 854.042 ?m,the sedimentation rate is 66.28 m/h,the aerobic rate is 46.66 mgO2/(g MLVSS·h),and the SVI is below 25 mL/g.During stable operation,the removal rates of COD,NH4+-N,and TP in the effluent were greater than 95%,97.6%,and 90%.Analyze the problems in the operation stage of fully granulated aerobic granular sludge,and take corresponding measures to restore the system to normal.The main contents include the following three aspects:(1)White granule proliferation phenomenon.In this experiment,the method of shortening the ST and changing the way of mud removal is combined to achieve the purpose of removing white granules.It was removed on the 146th day after the appearance of white granules.On the 170th day,the TN effluent removal rate was about 80%,and the reaction system returned to normal.According to the high-throughput analysis of MiSeq,the dominant bacteria in the yellow granules is a typical GAO(Candidatus_Competibacter),while the anaerolineaceae(Anaerolineaceae)is the dominant bacteria in the white granules,The relatively low abundance of Competibacter is the main reason for the loose granule shape,good light transmission and white granules.(2)Filamentous bacteria over-proliferation.In this experiment,the purpose of removing filamentous bacteria was achieved by combining increasing the length of anaerobic cycle and increasing the influent phosphorus concentration.On the 10th day after changing the cycle duration and the influent TP concentration,the SVI30 value was 16.87 mL/g,and the removal rates of COD,TN and TP in the effluent were greater than 92%,76.2%and 93.3%.Filamentous bacteria proliferate excessively,competing with functional bacteria for nutrients,resulting in the loss of advantages of a large number of strains in competition,and the microbial diversity of filamentous bacteria granules is significantly lower than that of normal granules.(3)The granules age and disintegrate.The anaerobic cavity appeared inside the larger granule size,and the large granule disintegration occurred on the 355th day.The effluent sludge concentration reached 0.125 g/L,and the sludge concentration gradually decreased.After storage for 21 days in a refrigerator at 4?,the granules no longer disintegrated after restarting for 5 days,the sludge concentration rose,and the system gradually returned to normal operation.