Modelling and Experiments on Fluidized-Bed Biofilm Reactors

Bignami, L.; Eramo, Barbara; Gavasci, Renato; Ramadori, R.; Rolle, E.

doi:10.2166/wst.1991.0184

Cited by 14 publications

(3 citation statements)

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“…Challenges to rigorous modeling of FBBs arise from complex hydrodynamics, variable biofilm structure and morphology, poor understanding of processes affecting rate of substrate degradation, microbial population changes, and loss of biomass from reactors. Models that have been developed to describe rate of substrate uptake by microbial populations in FBBs generally rest upon assumptions that include: a homogeneous biofilm, equal biofilm thickness on all carrier particles throughout the fluidized bed, Fick's Law of diffusion inside the biofilm, and Monod kinetics of substrate utilization in the biofilm (Andrews and Trepasso, 1985;Arvin and Harremoes, 1990;Bignami et al, 1991;He and Ping, 1994;Heath et al, 1990;Fan, 1989;Kim, 1992).…”

Section: Introductionmentioning

confidence: 99%

Effects of stratification in a fluidized bed bioreactor during treatment of metalworking wastewater

Schreyer

Coughlin

1999

Biotechnol. Bioeng.

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During wastewater treatment, biofilm‐coated sand particles stratified in a fluidized bed bioreactor (FBB); particles coated by thicker biofilm segregated toward the top of the bed. Stratification was so well developed that at least two co‐existing regions of significantly different mean biofilm thickness were visually distinct within the operating FBB. The observed stratification is attributed to differences in forces of drag, buoyancy, shear, and collisional impact, as well as differences of collision rate within the different regions. Particles with thick biofilm (thickness >100 μm) near the top of the bed consumed substrate at significantly lower rates per unit biomass than particles with thin biofilm (10–20 μm) near the bottom of the bed, thereby suggesting that substrate mass‐transfer resistance through biofilm may limit biodegradation rates in the upper portion of the FBB. Large agglomerates of biomass floc and sand, which formed at the top of the fluidized bed, and sand particles with thick biofilm were susceptible to washout from the FBB, causing operational and treatment instability. Radial injection of supplemental liquid feed near the top of the bed increased shear and mixing, thereby preventing formation and washout of agglomerates and thickly coated sand particles. Supplemental liquid injection caused the mean specific biomass loading on the sand to increase and also increased the total biomass inventory in the FBB. Rates of biodegradation in the FBB appeared to be limited by penetration of substrates into the biofilm and absorption of oxygen from air into the wastewater. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 63: 129–140, 1999.

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Section: Introductionmentioning

confidence: 99%

Effects of stratification in a fluidized bed bioreactor during treatment of metalworking wastewater

Schreyer

Coughlin

1999

Biotechnol. Bioeng.

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“…They stated that the oxygen transfer in a microcarrier system is usually gas/liquid mass-transfer limited. Bliem et al (1988) proposed a critical radius of 300-700 m. Bignami et al (1991) presented a biofilm model based on the boundary condition that an oxygen gradient between pellet surface and bulk liquid does not exist. They also distinguished an active biofilm layer near the surface and an underlying inactive radius of limited conditions.…”

Section: Discussionmentioning

confidence: 99%

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Preissmann

Wiesmann²,

Buchholz

et al. 1997

Cytotechnology

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Macroporous microcarriers are commonly applied to fixed and fluidized bed bioreactors for the cultivation of stringent adherent cells. Several investigations showed that these carriers are advantageous in respect to a large surface area (Griffiths, 1990; Looby, 1990a).When growing a rC-127 cell line on Cytoline 2 (Pharmacia Biotech), no satisfactory product yield could be achieved. A possible limitation in the supply of nutrient components was investigated to explain these poor results. No significant concentration gradients could be detected. Nevertheless, fluorescence staining revealed a decreasing viability, particularly inside the macroporous structure. Therefore, oxygen transfer to and into the carriers was examined by means of an oxygen microprobe during the entire process. Additional mathematical modeling supported these results.The maximum penetration depth of oxygen was determined to be 300 μm. A critical value influencing the oxygen uptake rate of the rC-127 cells occured at a dissolved oxygen concentration of 8% of air saturation. A significant mass transfer resistance within a laminar boundary film at the surface of the carrier could be detected. This boundary layer had a depth of 170 μm. The results showed that even a 40% air saturation in the bulk liquid could not provide an efficient oxygenation of the surface biofilm during the exponential growth phase. Fluorescent staining reveals a poor viability of cells growing inside the carrier volume. Thus, oxygen supply limits the growth of rC-127 cells on macroporous microcarriers. Poor process performance and low product yield could be explained this way.

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“…Los materiales de soporte de baja densidad permiten la expansión del lecho hasta en un 100% bajo tasas de recirculación menores a las requeridas para arena o carbón activado (Trinet et al, 1991;Bignami et al, 1991). Tavares et al, (1995) reportaron el uso de una resina con la que prepararon partículas de 2.7 mm de diámetro y densidad de 1180 kg m -3 resultando fácilmente fluidizables y con buena capacidad de fijación de biopelícula.…”

Section: Introductionunclassified

Materiales de soporte para el crecimiento de biopelícula en un reactor de lecho fluidizado

́án¹,

Nevárez-Moorillón²,

Bautista-Margulis³

et al. 2018

tecnociencia

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Se evaluó el efecto de materiales de soporte de baja densidad sobre la eficiencia de un reactor de lecho fluidizado para el tratamiento de aguas residuales. Primero se seleccionaron varios materiales de origen mineral, con densidad específica menor que la densidad de la arena sílica. Después se evaluaron otros materiales porosos de densidad específica ligeramente menor a la densidad de la arena sílica, pero con una densidad aparente significativamente menor. De un total de 10 materiales evaluados, sobresalieron la mezcla de poliéster-perlita expandida y la perlita vitrificada como los mejores materiales. La fluidización del lecho de poliéster-perlita se obtuvo con una velocidad de recirculación de 0.45 y la de perlita vitrificada con 0.55 cm seg-1. Ambas velocidades de recirculación son menores a las reportadas para materiales de densidad similar. El régimen de fluidización favoreció la operación del reactor en forma continua sin la necesidad de aplicar lavados del lecho y sin llegar a la saturación del mismo. DOI: https://doi.org/10.54167/tecnociencia.v2i2.74

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Modelling and Experiments on Fluidized-Bed Biofilm Reactors

Cited by 14 publications

References 0 publications

Effects of stratification in a fluidized bed bioreactor during treatment of metalworking wastewater

Effects of stratification in a fluidized bed bioreactor during treatment of metalworking wastewater

Untitled

Materiales de soporte para el crecimiento de biopelícula en un reactor de lecho fluidizado

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