| Bacterial Extracellular polymeric substances(EPS)will affect the physical and chemical properties of the sludge,such as the surface properties,adsorption performance,settling performance,and the formation and stability of granular sludge,which in turn affects the sewage treatment system’s efficiency in treating pollutants,and in different flow regimes The content of EPS secreted by microorganisms is different.This topic aims to compare two EPS extraction methods and choose the best method for the subsequent experiments to extract EPS;and to study the influence mechanism of flow field changes on EPS secretion in the sludge system,by investigating the sludge system During operation,the removal efficiency of pollutants,the physical and chemical properties of sludge,the structure of microbial community,and the change law of EPS content,combined with computational fluid dynamics to simulate the flow characteristics of the reactor,analyze the changes of EPS content in the sludge system under different flow conditions and The law of interaction between the microbial community structure.Aiming at the problem of how to choose an extraction method that can extract EPS efficiently and less damage to cells,the total amount of EPS extracted by the thermal extraction method and the cation exchange resin method(CER method)under different conditions and its effect on the cells are compared.It is found that the content of EPS extracted by the thermal extraction method under different conditions is higher than 150 mg/g VSS,while the content of EPS extracted by the CER method under different conditions is in the range of 90～120 mg/g VSS;The degree of damage to microbial cells by the extraction method is also relatively higher.Compared with other methods,the thermal extraction method with a centrifugal force of 4000×g,a centrifugal time of 10 min,a heating temperature of 60°C,and a heating time of 15 min can extract as much EPS as possible and damage the microbial cells as much as possible.smaller.Aiming at the problem of how the flow field affects the EPS secretion of the activated sludge system,it was discovered after 27 days of operation of three activated sludge reactors with apparent gas velocities of 0.66 cm/s,0.46 cm/s,and 0.26 cm/s.Changes in the flow field will result in a large difference in the structure of the microbial community in the reaction system and the relative abundance of the functional flora,which in turn will lead to differences in the treatment efficiency of pollutants and the sludge EPS content of the three reaction systems;On 27 days,the EPS of the sludge in the reactor operating at a superficial gas velocity of 0.66 cm/s reached 127.83 mg/g VSS,which was much higher than the initial value,while the EPS content of the other two systems was lower than 40 mg/g VSS;And,within the range of 0.26～0.66 cm/s of apparent gas velocity in the system,as the apparent gas velocity increases,the relative abundance of EPS-producing bacteria in the reaction system increases,and the EPS content of the sludge in the system also increases.increase.Aiming at the problem of how the flow field affects the EPS secretion of the aerobic granular sludge system,three aerobic granular sludges with apparent gas velocities of 1.74 cm/s,2.33 cm/s,and 2.91 cm/s were reacted by running for 69 days.After the reactor,it was found that during the entire operation,the three reaction systems all showed good pollutant removal effects,the effluent COD concentration was all lower than 75 mg/L,the ammonia nitrogen concentration was all lower than20 mg/L,and the three reaction systems On the 20 th day of operation,the average particle size of the sludge volume measured was higher than 200 μm,forming aerobic granular sludge.Changes in the flow field led to different changes in the total amount of EPS in the system and a large difference in the structure of microbial communities.The EPS content of the sludge in the three reaction systems was on the 45 th day(156.34 mg/g VSS)and the 9th day(194.63 mg/g VSS),the maximum value on day6(151.12 mg/g VSS),and the reactor running at a superficial gas velocity of 2.91cm/s compared with the reactor running at 1.74 cm/s and 2.33 cm/s In other words,after 40 days of operation,the EPS content of the sludge in the system was significantly higher,which was caused by the different relative abundance of EPSproducing bacteria in the system;for the better oxygen granular sludge system,the flow field change has an effect on the activated sludge system.The impact is greater. |
PDF Full Text Request