Biological Fluidized Beds Containing Widely Different Bioparticles

Ro, Kyoung S.; Neethling, J.B.

doi:10.1061/(asce)0733-9372(1994)120:6(1416)

Cited by 22 publications

(13 citation statements)

References 8 publications

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“…Since the feeding is from the bottom of the reactor, these granules get a higher substrate load and therefore a higher radius, which enhances the segregation effect. Segregation of biomass has been reported earlier and is hence a common occurrence in wastewater treatment based on granular sludge or biofilms (Di Felice et al, 1997;Ro and Neethling, 1994). Selective sludge withdrawal from either top or bottom of the sludge bed can therefore be used as a possibility to control the microbial community structure granular sludge technology.…”

Section: Discussionmentioning

confidence: 90%

Temperature and salt effects on settling velocity in granular sludge technology

et al. 2012

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Settling velocity is a crucial parameter in granular sludge technology. In this study the effects of temperature and salt concentrations on settling velocities of granular sludge particles were evaluated. A two-fold slower settling velocity for the same granules was observed when the temperature of water decreases from 40 °C to 5 °C. Settling velocities also decreased with increasing salt concentrations. Experiments showed that when granules were not pre-incubated in a solution with increased salt concentration, they initially floated. The time dependent increase in mass and hence in settling speed of a granule due to salt diffusion into the granule was dependent on the granule diameter. The time needed for full salt equilibrium with the bulk liquid took 1 min for small particles from the top of the sludge bed and up to 30 min for big granules from the bottom of the sludge bed. These results suggest that temperature and salt concentration are important parameters to consider in the design, start-up and operation of granular sludge reactors and monitoring of these parameters will aid in a better control of the sludge management in anaerobic and aerobic granular sludge technology. The observations also give an explanation for previous reports which were suggesting that a start-up of granular sludge reactors is more difficult at low temperatures.

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Section: Discussionmentioning

confidence: 90%

Temperature and salt effects on settling velocity in granular sludge technology

et al. 2012

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“…Many authors (Ro and Neethling, 1994;Safferman and Bishop, 1996;Schreyer and Coughlin, 1999;Trinet et al, 1991) observed that the bed becomes stratified due to the presence of granules with different biofilm thicknesses. In such a context, the application of the Richardson and Zaki correlation remains dubious.…”

Section: Discussionmentioning

confidence: 99%

“…The biofilm also increases the particle's size thereby increasing the drag force exerted on it by the liquid flowing upward. The particles in a fluidized bed are expected to segregate according to size and mean density (Ro and Neethling, 1994;Safferman and Bishop, 1996;Trinet et al, 1991).…”

Section: Bed Stratificationmentioning

confidence: 99%

Modelling anaerobic biofilm reactors—A review

Saravanan

Sreekrishnan

2006

Journal of Environmental Management

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“…Irregular shapes of suspended biofilm pellets and granules are quite common. They often resemble spheres, ellipsoids, or disks; sometimes they are needlelike, knobby, or com-pletely irregular (Alphenaar, 1994;Csikor et al, 1994;Diekman et al, 1990;Gjaltema et al, 1995;MacLeod et al, 1990;Peereboom and Vereijken, 1994;Quarmby and Forster, 1995;Ro and Neethling, 1994;Tijhuis et al, 1996). The advantage of a bioparticle not being spherical is clear:…”

Section: Biofilm Shapementioning

confidence: 99%

Abrasion of suspended biofilm pellets in airlift reactors: Importance of shape, structure, and particle concentrations

Gjaltema

Vinke

Loosdrecht

et al. 1997

Biotechnol. Bioeng.

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The detachment of biomass from suspended biofilm pellets in three‐phase internal loop airlift reactors was investigated under nongrowth conditions and in the presence of bare carrier particles. In different sets of experiments, the concentrations of biofilm pellets and bare carrier particles were varied independently. Gas hold‐up, bubble size, and general flow pattern were strongly influenced by changes in volume fractions of biofilm pellets and bare carrier particles. In spite of this, the rate of biomass detachment was found to be linear with both the concentration of biofilm pellets and the bare carrier concentration up to a solids hold‐up of 30%. This implies that the detachment rate was dominated by collisions between biofilm pellets and bare carrier particles. These collisions caused an on‐going abrasion of the biofilm pellets, leading to a reduction in pellet volume. Breakage of the biofilm pellets was negligible. The biofilm pellets were essentially ellipsoidal, which made three‐dimensional size determination necessary. Calculating particle volumes from two‐dimensional image analysis measurements and assuming a spherical shape led to serious errors. The abrasion rate was not equal on all sides of the biofilm pellets, resulting in an increasing flattening of the pellets. This flattening was oriented with the basalt carrier inside the biofilm and independent of the absolute abrasion rate. These observations suggest that the collisions causing abrasion are somehow oriented. The internal structure of the biofilms showed two layers, a cell‐dense outer layer and an interior with a low biomass density. Taking this density gradient into account, the washout of detached biomass matched observed changes in volume of the biofilm pellets. No gradient in biofilm strength with biofilm depth was indicated. © 1997 John Wiley & Sons, Inc.

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Biological Fluidized Beds Containing Widely Different Bioparticles

Cited by 22 publications

References 8 publications

Temperature and salt effects on settling velocity in granular sludge technology

Temperature and salt effects on settling velocity in granular sludge technology

Modelling anaerobic biofilm reactors—A review

Abrasion of suspended biofilm pellets in airlift reactors: Importance of shape, structure, and particle concentrations

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