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  • 1
    Electronic Resource
    Electronic Resource
    A structured metabolic model for anaerobic and aerobic stoichiometry and kinetics of the biological phosphorus removal process (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 277-287 
    Details
    ISSN: 0006-3592
    Keywords: phosphorus removal ; biological ; kinetics ; metabolic model ; polyphosphate ; PHB ; glycogen ; batch reactor, sequenced ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A structured metabolic model is developed that describes the stoichiometry and kinetics of the biological P removal process. In this approach all relevant metabolic reactions underlying the metabolism, considering also components like adenosine triphosphate (ATP) and nic-otinamide-adenine dinucleotide (NADH2) are describedbased on biochemical pathways. As a consequence of the relations between the stoichiometry of the metabolic reactions and the reaction rates of components, the required number of kinetic relations to describe the process is reduced. The model describes the dynamics of the storage compounds which are considered separately from the active biomass. The model was validated in experiments at a constant sludge retention time of 8 days, over the anaerobic and aerobic phases in which the external oncentrations as well as the internal fractions of the relevant components involved in the P-removal process were monitored. These measurements include dissolved acetate, phosphate, and ammonium; oxygen consumption; poly-β-hydroxybutyrate (PHB); glycogen; and active biomass. The model satisfactorily describes the dynamic behavior of all components during the anaerobicand aerobic phases.© 1995 John Wiley & Sons, Inc
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260470302
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A metabolic model of the biological phosphorus removal process: II. Validation during start-up conditions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 234-245 
    Details
    ISSN: 0006-3592
    Keywords: phosphorus removal, biological ; metabolic model ; polyphosphate ; PHB, ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A metabolic model of the biological phosphorus removal process has been developed and validated previously for complex conversions during the process under anaerobic and aerobic conditions at different growth rates in sequencing batch reactors in steady state. For additional validation of the metabolic model, the model was applied to the dynamic conditions which occur during the start-up phase of the biological P removal in the presence and absence of non-polyP heterotrophic microorganisms. In a laboratory scale sequencing batch reactor, experiments were performed to examine the enrichment of the population with polyphosphate organisms during the start-up and the subsequent shift from non-polyP, heterotrophic organisms to polyP organisms in the sludge. The effect of different influent loading patterns for acetate and phosphate was studied. In these experiments, the maximal growth rate of the polyP organisms and the behavior of the internal storage compounds could be derived. The metabolic model was capable of describing the experimental results, without the need to adjust the kinetic or stoichiometric parameters obtained under steady state conditions. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480310
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Model of the anaerobic metabolism of the biological phosphorus removal process: Stoichiometry and pH influence (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 461-470 
    Details
    ISSN: 0006-3592
    Keywords: phosphorus removal ; metabolic model ; stoichiometry ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the anaerobic phase of a biological phosphorus removal process, acetate is taken up and converted to PHB utilizing both energy generated in the degradation of polyphosphate to phosphate, which is released, and energy generated in the conversion of glycogen to poly-β-hydroxy butyrate (PHB). The phosphate/acetate ratio cannot be considered a metabolic constant, because the energy requirement for the uptake of acetate is strongly influenced by the pH value. The observed phosphate/acetate ratio shows a variation of 0.25 to 0.75 P-mol/C-mol in a pH range of 5.5 to 8.5. It is shown that stored glycogen takes part in the metabolism to provide reduction equivalents and energy for the conversion of acetate to PHB. A structured metabolic model, based on glycogen as the source of the reduction equivalents in the anaerobic phase and the effect of the pH on the energy requirement of the uptake of acetate, is developed. The model explains the experimental results satisfactorily. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430605
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  • 4
    Electronic Resource
    Electronic Resource
    A metabolic model of the biological phosphorus removal process: I. Effect of the sludge retention time (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 222-233 
    Details
    ISSN: 0006-3592
    Keywords: phosphorus removal, biological ; metabolic model ; polyphosphate ; PHB, glycogen ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The biological phosphorus removal process is a process which depends basically on three internal storage compounds. Poly-β-hydroxybutyrate (PHB) produced during the anaerobic phase is used as substrate for biomass, polyphosphate, and glycogen formation. The reaction rates of the aerobic processes are primarily determined by the PHB content of the cells. This PHB content is highly dynamic due to the conversions during the anaerobic and aerobic phase of the cycle and the ratio between substrate addition and biomass present in the reactor. The amount of biomass present in the reactor is determined by the sludge retention time and growth rate. A metabolic model of the biological phosphorus removal process was developed and verified over a wide range of growth rates. The effect of different growth rates on the internal fractions of stored components was determined and described mathematically. One set of kinetic parameters was capable of describing the measured conversions of all components observed in the reactor as a function of the sludge retention time. © 1995 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480309
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  • 5
    Electronic Resource
    Electronic Resource
    Detachment of biomass from suspended nongrowing spherical biofilms in airlift reactors (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 258-269 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; detachment ; abrasion ; breakage ; airlift reactor ; hydrodynamics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In three-phase internal loop airlift reactors, the detachment of biomass from suspended biofilm pellets in the presence of bare carrier particles was investigated under nongrowth conditions. The detachment rate was dominated by collisions between bare carrier particles and biofilm pellets. The concentration of bare carrier particles and the carrier roughness strongly influenced the detachment rate. A change in flow regime from bubbling to slug flow considerably increased the detachment rate. Otherwise, the superficial gas velocity did not directly affect the detachment rate. The influence of particle size was not clear. The bottom clearance did not affect the detachment rate within the tested range. Other aspects of reactor geometry might be important. The main detachment processes were abrasion and breakage of biofilm pellets. During the detachment process, two phases could be distinguished. In the first phase the detachment was relatively high, and both breakage and abrasion of biofilm pellets occurred. During the second phase, breakage dominated and the detachment rate was lower. The two-phase behavior is explained by differences in strength between the inner and outer biofilm layers, possibly caused by variations in local growth rates during biofilm formation. Differences in growth history might also explain the various detachment rates observed with different biofilm batches. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260460309
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  • 6
    Electronic Resource
    Electronic Resource
    Hydrodynamic characteristics and gas-liquid mass transfer in a biofilm airlift suspension reactor (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 627-635 
    Details
    ISSN: 0006-3592
    Keywords: airlift reactor ; biofilm ; hydrodynamics ; mass transfer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The hydrodynamics and mass transfer, specifically the effects of gas velocity and the presence and type of solids on the gas hold-up and volumetric mass transfer coefficient, were studied on a lab-scale airlift reactor with internal draft tube. Basalt particles and biofilm-coated particles were used as solid phase. Three distinct flow regimes were observed with increasing gas flow rate. The influence of the solid phase on the hydrodynamics was a peculiar characteristic of the regimes. The volumetric mass transfer coefficient was found to decrease with increasing solid loading and particle size. This could be predominantly related to the influence that the solid has on gas hold-up. The ratio between gas hold-up and volumetric mass transfer coefficient was found to be independent of solid loading, size, or density, and it was proven that the presence of solids in airlift reactors lowers the number of gas bubbles without changing their size. To evaluate scale effects, experimental results were compared with theoretical and empirical models proposed for similar systems. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 627-635, 1998.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    A metabolic model for biological phosphorus removal by denitrifying organisms (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 52 (1996), S. 685-695 
    Details
    ISSN: 0006-3592
    Keywords: phosphorus removal ; denitrifying dephosphatation ; stoichiometry ; metabolic model ; sequencing batch reactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A metabolic model for biological phosphorus removal under denitrifying conditions has been established. The model is based on previous work with aerobic phosphorus removal. The form of the kinetic equations used is the same as for the aerobic model. The main difference is the value of P/NADH2 ratio in the electron transport phosphorylation with nitrate (δN). This value was determined independently from batch tests with an enriched culture of denitrifying phosphorus-removing bacteria. The measured δN was approximately 1.0 mol ATP/mol NADH2. This indicates that the energy production efficiency with nitrate compared to oxygen is approximately 40% lower. These batch tests were also used to identify a proper set of kinetic parameters. The obtained model was subsequently applied for the simulation of cyclic behavior in an anaerobic-anoxic sequencing batch reactor at different biomass retention times. The simulation results showed that the metabolic model can be used successfully for the denitrifying dephosphatation process. The obtained kinetic parameters for denitrifying enrichment cultures, however, deviated from those obtained for the aerobic enrichment cultures. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 8
    Electronic Resource
    Electronic Resource
    Abrasion of suspended biofilm pellets in airlift reactors: Importance of shape, structure, and particle concentrations (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 88-99 
    Details
    ISSN: 0006-3592
    Keywords: biofilm structure ; detachment ; abrasion ; collisions ; airlift-reactor ; hydrodynamics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 9
    Electronic Resource
    Electronic Resource
    An integrated metabolic model for the aerobic and denitrifying biological phosphorus removal (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 54 (1997), S. 434-450 
    Details
    ISSN: 0006-3592
    Keywords: biological phosphorus removal ; anaerobic-denitrifying process ; anaerobic-aerobic process ; denitrification ; activated sludge ; metabolic model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this work, an integrated metabolic model for biological phosphorus removal is presented. Using a previously proposed mathematical model it was shown to be possible to describe the two known biological phosphorus removal processes, under aerobic and denitrifying conditions, with the same biochemical reactions, where only the difference in electron acceptor (oxygen and nitrate) is taken into account. Though, apart from the ATP/NADH ratio, the stoichiometry in those models is identical, different kinetic parameters were found. Therefore, a new kinetic structure is proposed that adequately describes phosphorus removal under denitrifying and aerobic conditions with the same kinetic equations and parameters. The ATP/NADH ratio (δ) is the only model parameter that is different for aerobic and denitrifying growth. With the new model, simulations of anaerobic/aerobic and anaerobic/denitrifying sequencing batch reactors (A2 SBR and A/O SBR) were made for verification of the model. Not only short-term behavior, but also steady state, was simulated. The results showed very good agreement between model predictions and experimental results for a wide range of dynamic conditions and sludge retention times. Sensitivity analysis shows the influence of the model parameters and the feed substrate concentrations on both systems. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 434-450, 1997.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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