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Sludge Blanket Reactors (sludge + blanket_reactor)
Selected AbstractsMicroscopic observation of aerobic granulation in sequential aerobic sludge blanket reactorJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2001J.-H. Tay Aims: This paper attempts to provide visual evidence of how aerobic granulation evolves in sequential aerobic sludge blanket reactors. Methods and Results: A series of experiments were conducted in two column-type sequential aerobic sludge reactors fed with glucose and acetate as sole carbon source, respectively. The evolution of aerobic granulation was monitored using image analysis and optical and scanning electron microscopy. The results indicated that the formation of aerobic granules was a gradual process from seed sludge to compact aggregates, further to granular sludge and finally to mature granules with the sequential operation proceeding. Glucose- and acetate-fed granules have comparable characteristics in terms of settling velocity, size, shape, biomass density and microbial activity. However, the microbial diversity of the granules was associated with the carbon source supplied. In this work, an important aerobic starvation phase was identified during sequential operation cycles. It was found that periodical aerobic starvation was an effective trigger for microbial aggregation in the reactor and further strengthened cell,cell interaction to form dense aggregates, which was an essential step of granulation. The periodical starvation-induced aggregates would finally be shaped to granules by hydrodynamic shear and flow. Conclusions: Aerobic granules can be formed within 3 weeks in the systems. The periodical starvation and hydrodynamic conditions would play a crucial role in the granulation process. Significance and Impact of the Study: Aerobic granules have excellent physical characteristics as compared with conventional activated sludge flocs. This research could be helpful for the development of an aerobic granule-based novel type of reactor for handling high strength organic wastewater. [source] Effects of cationic polymer on start-up and granulation in upflow anaerobic sludge blanket reactorsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2004Ying Wang Abstract The upflow anaerobic sludge blanket (UASB) has been used successfully to treat a variety of industrial wastewaters. It offers a high degree of organics removal, low sludge production and low energy consumption, along with energy production in the form of biogas. However, two major drawbacks are its long start-up period and deficiency of active biogranules for proper functioning of the process. In this study, the influence of a coagulant polymer on start-up, sludge granulation and the associated reactor performance was evaluated in four laboratory-scale UASB reactors. A control reactor (R1) was operated without added polymer, while the other three reactors, designated R2, R3 and R4, were operated with polymer concentrations of 5 mg dm,3, 10 mg dm,3 and 20 mg dm,3, respectively. Adding the polymer at a concentration of 20 mg dm,3 markedly reduced the start-up time. The time required to reach stable treatment at an organic loading rate (OLR) of 4.8 g COD dm,3 d,1 was reduced by more than 36% (R4) as compared with both R1 and R3, and by 46% as compared with R2. R4 was able to handle an OLR of 16 g COD dm,3 d,1 after 93 days of operation, while R1, R2 and R3 achieved the same loading rate only after 116, 116 and 109 days respectively. Compared with the control reactor, the start-up time of R4 was shortened by about 20% at this OLR. Granule characterization indicated that the granules developed in R4 with 20 mg dm,3 polymer exhibited the best settleability and methanogenic activity at all OLRs. The organic loading capacities of the reactors were also increased by the addition of polymer. The maximum organic loading of the control reactor (R1) without added polymer was 19.2 g COD dm,3 d,1, while the three polymer-assisted reactors attained a marked increase in organic loading of 25.6 g COD dm,3 d,1. Adding the cationic polymer could result in shortening of start-up time and enhancement of granulation, which may in turn lead to improvement in the efficiency of organics removal and loading capacity of the UASB system. Copyright © 2004 Society of Chemical Industry [source] Hydrodynamics of upflow anaerobic sludge blanket reactorsAICHE JOURNAL, Issue 2 2009Ting-Ting Ren Abstract The hydrodynamic characteristics of upflow anaerobic sludge blanket (UASB) reactors were investigated in this study. A UASB reactor was visualized as being set-up of a number of continuously stirred tank reactors (CSTRs) in series. An increasing-sized CSTRs (ISC) model was developed to describe the hydrodynamics of such a bioreactor. The gradually increasing tank size in the ISC model implies that the dispersion coefficient decreased along the axial of the UASB reactor and that its hydrodynamic behavior was basically dispersion-controlled. Experimental results from both laboratory-scale H2 -producing and full-scale CH4 -producing UASB reactors were used to validate this model. Simulation results demonstrate that the ISC model was better than the other models in describing the hydrodynamics of the UASB reactors. Moreover, a three-dimensional computational fluid dynamics (CFD) simulation was performed with an Eulerian-Eulerian three-phase-fluid approach to visualize the phase holdup and to explore the flow patterns in UASB reactors. The results from the CFD simulation were comparable with those of the ISC model predictions in terms of the flow patterns and dead zone fractions. The simulation results about the flow field further confirm the discontinuity in the mixing behaviors throughout a UASB reactor. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] The role of cellular polysaccharides in the formation and stability of aerobic granulesLETTERS IN APPLIED MICROBIOLOGY, Issue 3 2001J.-H. Tay Aims:,This paper attempts to investigate the role of cellular polysaccharides in the formation and stability of aerobic granules. Methods and Results:,Three column sequential aerobic sludge blanket reactors (R1, R2 and R3) were operated at a superficial air upflow velocity of 0·3 cm s,1, 1·2 cm s,1 and 2·4 cm s,1, respectively. Aerobic granules appeared at cycle 42 in R2 and R3 with a mean size of 0·37 mm in R2 and 0·35 mm in R3, however, aerobic granulation was not observed in R1. After the formation of aerobic granules, the sludge volume index (SVI) decreased to 55 ml g,1 in R2 and 46 ml g,1 in R3. Aerobic granulation was concurrent with a sharp increase of cellular polysaccharides normalized to cellular proteins, which increased from 5·7 to 13·0 mg per mg proteins in R2, and 7·5,13·9 mg per mg protein in R3. The content of polysaccharides in aerobic granules was 2,3 times higher than that in the bioflocci cultivated in R1. The disappearance of aerobic granules in R2 was tightly coupled to a drop in cellular polysaccharides. After the reappearance of bioflocci in R2, the content of cellular polysaccharides were found to be restored to the level observed in R1. Conclusions:,It appears that the production of cellular polysaccharides could be stimulated by hydrodynamic shear force and contributes to the formation and stability of aerobic granules. Significance and Impact of the Study:,It is expected that this study would provide useful information for better understanding the mechanisms of aerobic granulation. [source] | |||||||||||||