The influence of substrate transport limitation on porosity and methanogenic activity of anaerobic sludge granules

Alphenaar, P.A.; Pérez, Montserrat; Lettinga, G.

doi:10.1007/bf00228619

Cited by 56 publications

(25 citation statements)

References 13 publications

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“…No relation was found between the affinity constant and the granule diameter, something expected if it is taken into account that only the outer layer of the granule was active. 19 In another study, 11 the same acetoclastic methanogenic activity in both intact and disintegrated granules was observed, although very small granules (0.44 mm) were employed.…”

Section: Introductionmentioning

confidence: 65%

“…Therefore, it can be reasonably assumed that concentration in the bulk liquid is almost equal to the concentration in the outer layer of the granule. Consequently, it can be considered that concentration in the inner part is negligible, since there are evidences in literature 19,33 that mentioned an inert zone in the core of the granules. This is caused because substrate does not reach deep layers, causing bacterial death by starvation.…”

Section: Description Of the Modelmentioning

confidence: 99%

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Explaining the enhanced performance of pulsed bioreactors by mechanistic modeling

et al. 2008

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in Wiley InterScience (www.interscience.wiley.com).In this work, steady-state mass balance based models were applied to two UASB reactors and three UAF for a better understanding of the role of pulsation on the efficacy improvement. Models were defined taking into account the hydraulic behavior of each digester and the limiting mechanism of the overall process kinetics (mass transfer or biochemical reaction rate). The application of the model allows to identify that mass transfer was the controlling step in all the reactors, except for the nonpulsed UASB, where methanogenic activity controlled the reactor performance in the last operation steady states. Mass transfer coefficients were higher for pulsed reactors and, in general, a good agreement between those estimated by an empirical correlation and from the model was obtained. Damko¨hler number values supported that the external mass transfer resistance was not negligible with respect to the process kinetic and in addition, in most cases, it controls the overall process in the reactors. The relative importance of external and internal mass transfer rate was calculated through the Biot number. The values of this dimensionless module indicated that external transport was the main contributor to overall mass transfer resistance.

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Section: Introductionmentioning

confidence: 65%

Section: Description Of the Modelmentioning

confidence: 99%

Explaining the enhanced performance of pulsed bioreactors by mechanistic modeling

et al. 2008

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“…Substrate transport limitations could affect the contact between substrate and methanogens in the core of biogranules, which were of major concern in the study of SMA [26,27]. As for UASB reactors treating high-calcium-content wastewater, significant losses of methanogenic activity were reported to have been caused by calcium precipitation [7,8].…”

Section: Location Of Calcium Precipitation and Smamentioning

confidence: 98%

Effect of wastewater composition on the calcium carbonate precipitation in upflow anaerobic sludge blanket reactors

Yang

Liu

et al. 2010

Front. Environ. Sci. Eng. China

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Calcium carbonate often precipitates in anaerobic reactors treating wastewater with high calcium content. The aim of this paper is to study the effect of wastewater composition on calcium carbonate precipitation in upflow anaerobic sludge blanket (UASB) reactors. Two laboratory-scale UASB reactors were operated with calcium-containing influents using acetate and carbohydrate as substrate, respectively. There was an obvious accumulation of inorganic precipitate observed in the biogranules. Observations via scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) showed that the acclimated biogranules in the two reactors differed in microstructure. Calcium carbonate was found to have precipitated on the surface of acetate-degrading biogranules, but precipitated at the core of the carbohydrate-degrading biogranules. The results indicated that substrates had significant influence on the location of calcium carbonate precipitation in anaerobic granular sludge, which was expected due to the different methanogens distribution and pH gradient within the granular sludge degrading various substrates. Moreover, the location of calcium carbonate precipitation substantially affected the specific methanogenic activity (SMA) of the granular sludge. The SMA of the acetate-degrading biogranules dropped from 1.96 gCOD CH 4 %gVSS -1 %d -1 to 0.61 gCOD CH 4 %gVSS -1 %d -1 after 180-d of operation in the reactor. However, the SMA of the carbohydrate-degrading biogranules was not adversely affected by calcium carbonate precipitation.

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“…Alphenaar et al [4] reported that biomass granulation in an UASB reactor is favored by the combination of high-liquid upflow velocity and short hydraulic retention time (HRT). However, for successful start-up and stable operation of UASB reactors, the reactor HRT cannot be reduced below 6 h. For wastewaters where granulation is reported to be successful, mixing developed in the reactor is of immense significance [5].…”

Section: Introductionmentioning

confidence: 99%

“…Granulation in UASB reactors depends upon several parameters such as wastewater types [9][10][11]; seed sludge characteristics [12]; characteristics of cell surface [13]; temperature [14][15]; pH [16]; and organic loading rates [4]. However, under favorable wastewater types and environmental conditions, the success of granulation in the reactors for treating biodegradable organic wastewaters (free from toxicity) depends on the operating conditions, defining magnitude of mixing in the reactors.…”

Section: Introductionmentioning

confidence: 99%

Influence of biogas-induced mixing on granulation in UASB reactors

Bhunia

Ghangrekar

2008

Biochemical Engineering Journal

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The influence of substrate transport limitation on porosity and methanogenic activity of anaerobic sludge granules

Cited by 56 publications

References 13 publications

Explaining the enhanced performance of pulsed bioreactors by mechanistic modeling

Explaining the enhanced performance of pulsed bioreactors by mechanistic modeling

Effect of wastewater composition on the calcium carbonate precipitation in upflow anaerobic sludge blanket reactors

Influence of biogas-induced mixing on granulation in UASB reactors

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