Influence of the liquid-phase mass transfer on the performance of a packed-bed bioreactor for wastewater treatment

Sarti, Arnaldo; Vieira, L. G. T.; Foresti, Eugênio; Zaiat, Marcelo

doi:10.1016/s0960-8524(01)00025-6

Cited by 35 publications

(15 citation statements)

References 8 publications

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“…Packed-bed reactors presented better performance than those attained in microcosms due to high cell density, development of a biomass acclimated to BTEX degradation in the reactor (Shim & Yang 1999), minimization of the liquid-phase mass transfer resistance (Sarti et al 2001) and a suitable hydrodynamic pattern (Zaiat et al 1997).…”

Section: Resultsmentioning

confidence: 99%

Kinetics of BTEX degradation in a packed-bed anaerobic reactor

2006

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The ever-increasing diversity of industrial activity is responsible for the discharge of compounds that are toxic or difficult to degrade into the environment. Some of the compounds found in surface and ground waters, usually deriving from the contamination of oil-based products, are benzene, toluene, ethylbenzene and xylenes (BTEX). To remove these compounds from contaminated water, a bench-scale horizontal-flow anaerobic immobilized biomass reactor, containing anaerobic biomass from various sources immobilized in polyurethane foam matrices, was employed to treat a synthetic substrate composed of protein, carbohydrates and BTEX solution in ethanol, as well as a BTEX solution in ethanol as the sole carbon source. The reactor removed up to 15.0 mg/l of each BTEX compound over a hydraulic detention time of 11.4 h. A first-order kinetic model fitted the experimental data well, showing correlation coefficients higher than 0.994. The apparent first-order coefficient values, k1(app), ranged from 8.4+/-1.5 day(-1) for benzene to 10.7+/-1.4 day(-1) for o-xylene in the presence of ethanol, protein and carbohydrates, and from 10.0+/-2.0 day(-1) for benzene to 13.0+/-1.7 day(-1) for o-xylene in the presence of ethanol. The BTEX degradation rates estimated here were 10- to 94-fold higher than those found in reports on microcosm studies.

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Section: Resultsmentioning

confidence: 99%

Kinetics of BTEX degradation in a packed-bed anaerobic reactor

2006

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“…In classical biofilm systems (Mörsen and Rehm, 1987;Sarti et al, 2001) or in other support materials (Shim and Yang, 1999), the amount of immobilized cells in the reactor is proportional to the specific surface area of the support material. Cells are only immobilized on the outer surface of the support material even though they have a high porosity, since the flow effects/conditions in the reactor and existing mass transfer limitations through the biofilm prevent cell penetration and viability (Hem et al, 1994;Hirata et al, 1998;Erhan et al, 2004).…”

Section: Discussionmentioning

confidence: 99%

Bioprocess intensification in flow‐through monolithic microbioreactors with immobilized bacteria

Akay

Erhan

Keskinler

2005

Biotech & Bioengineering

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Microporous polymers (with porosity up to 90%) with a well-prescribed internal microstructure were prepared in monolithic form to construct a flow-through microbioreactor in which phenol-degrading bacteria, Pseudomonas syringae, was immobilized. Initially, bacteria was forced seeded within the pores and subsequently allowed to proliferate followed by acclimatization and phenol degradation at various initial substrate concentrations and flow rates. Two types of microporous polymer were used as the monolithic support. These polymers differ with respect to their pore and interconnect sizes, macroscopic surface area for bacterial support, and phase volume. Polymer with a nominal pore size of 100 microm with phase volume of 90% (with highly open pore structure) yielded reduced bacterial proliferation, while the polymer with nominal pore size of 25 microm with phase volume of 85% (with small interconnect size and large pore area for bacterial adhesion) yielded monolayer bacterial proliferation. Bacteria within the 25 microm polymer support remained monolayered, without any apparent production of extracellular matrix during the 30-day continuous experimental period. The microbioreactor performance was characterized in terms of volumetric utilization rate and compared with the published data, including the case where the same bacteria was immobilized on the surface of microporous polymer beads and used in a packed bed during continuous degradation of phenol. It is shown that at similar initial substrate concentration, the volumetric utilization in the microreactor is at least 20-fold more efficient than the packed bed, depending on the flow rate of the substrate solution. The concentration of the bacteria within the pores of the microreactor decreases from 2.25 cells per microm2 on the top surface to about 0.4 cells per microm2 within 3 mm reactor depth. If the bacteria-depleted part of the microreactor is disregarded, the volumetric utilization increases by a factor of 30-fold compared with the packed bed. This efficiency increase is attributed to the reduction of diffusion path for the substrate and nutrients and enhanced availability of the bacteria for bioconversion in the absence of biofilm formation as well as the presence of flow over the surface of the monolayer bacteria.

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“…In this study the results for Biot number are from 15 to 20. According to Sarti et al [17], the effect of external mass transfer resistance is not significant for Bi higher than 100. However, the values of Bi in this experiment were very low compared to the limit proposed by these authors.…”

Section: Adsorption-controlling Stepmentioning

confidence: 96%