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  • 1
    Digitale Medien
    Digitale Medien
    Biological phosphate removal processes (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 289-296 
    Details
    ISSN: 1432-0614
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Biological phosphate removal has become a reliable and well-understood process for wastewater treatment. This review describes the historical development of the process and the most important microbiological and process-engineering aspects. From a microbiological point of view, the role of␣poly(hydroxyalkanoates) as storage material in a dynamic process and the use of polyphosphate as an energy reserve are the most important findings. From a process-engineering point of view, the study of biological phosphate removal has shown that highly complex biological processes can be designed and controlled, provided that the importance of the prevailing microbiological ecological processes is recognised.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002530051052
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  • 2
    Digitale Medien
    Digitale Medien
    Effect of polyphosphate limitation on the anaerobic metabolism of phosphorus-accumulating microorganisms (1998)
    Springer
    Applied microbiology and biotechnology 50 (1998), S. 273-276 
    Details
    ISSN: 1432-0614
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract There are two types of microbial populations described in the literature as being capable of anaerobic storage of acetic acid in activated-sludge processes: the polyphosphate-accumulating organisms (PAO) and the glycogen-accumulating non-polyphosphate organisms (GAO). Both groups use the conversion of glycogen to poly-hydroxyalkanoate to produce ATP and NADH; however, the first group can also produce ATP from polyphosphate (poly-P). No representative pure cultures are available from either group. The question arises: is the observed activity of GAO due to PAO that are depleted in poly-P ? In this study, using a laboratory sequencing batch reactor containing an enriched culture, the ability of the enriched PAO to utilize organic substrate (acetate) anaerobically was investigated under conditions of poly-P limitation and surplus glycogen content of the biomass. This study showed clearly that, under these conditions, almost no acetate was taken up. Furthermore, this strongly suggests that PAO can not use glycogen conversion to poly-hydroxyalkanoate as the sole energy source under anaerobic conditions, which seems to be the restricted to a separate group of GAO. On the basis of the results and literature data, an improved scheme for the anaerobic acetate accumulation is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002530051289
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  • 3
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): phosphorus removal ; denitrifying dephosphatation ; stoichiometry ; metabolic model ; sequencing batch reactor ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: 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.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): biofilm structure ; detachment ; abrasion ; collisions ; airlift-reactor ; hydrodynamics ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: 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.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Influence of dissolved oxygen concentration on nitrite accumulation in a biofilm airlift suspension reactor (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 168-178 
    Details
    ISSN: 0006-3592
    Schlagwort(e): airlift reactor ; BAS reactor ; biofilm ; nitrification ; nitrite ; oxygen transfer ; residence time ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The biofilm airlift suspension (BAS) reactor can treat wastewater at a high volumetric loading rate combined with a low sludge loading. Two BAS reactors were operated, with an ammonium load of 5 kg N/(m3 d), in order to study the influence of biomass and oxygen concentration on the nitrification process. After start-up the nitrifying biomass in the reactors gradually increased up to 30 g VSS/L. Due to this increased biomass concentration the gas-liquid mass transfer coefficient was negatively influenced. The resulting gradual decrease in dissolved oxygen concentration (over a 2-month period) was associated with a concomitantly nitrite build-up. Short term experiments showed a similar relation between dissolved oxygen concentration (DO) and nitrite accumulation. It was possible to obtain full ammonium conversion with approximately 50% nitrate and 50% nitrite in the effluent. The facts that (i) nitrite build up occurred only when DO dropped, (ii) the nitrite formation was stable over long periods, and (iii) fully depending on DO levels in short term experiments, led to the conclusion that it was not affected by microbial adaptations but associated with intrinsic characteristics of the microbial growth system. A simple biofilm model based on the often reported difference of oxygen affinity between ammonium and nitrite oxydizers was capable of adequately describing the phenomena.Measurements of biomass density and concentration are critical for the interpretation of the results, but highly sensitive to sampling procedures. Therefore we have developed an independent method, based on the residence time of Dextran Blue, to check the experimental methods. There was a good agreement between procedures.The relation between biomass concentration, oxygen mass transfer rate and nitrification in a BAS reactor is discussed. © 1997 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): biofilm ; detachment ; abrasion ; breakage ; airlift reactor ; hydrodynamics ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: 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.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260460309
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  • 7
    Digitale Medien
    Digitale Medien
    A thermodynamically based correlation for maintenance gibbs energy requirements in aerobic and anaerobic chemotrophic growth (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 509-519 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Gibbs energy requirements ; chemotrophic growth ; maintenance ; anaerobic and aerobic ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A thermodynamic framework has been provided for the description of maintenance requirements of microorganisms. The central parameter is the biomass specific Gibbs energy consumption for maintenance, mE (kJ/C-mol biomass · h). A large set of data has been used including (i) a large range of different organisms (bacteria, yeasts, plant cells), (ii) mixed cultures, (iii) heterotrophic and autotrophic growth, (iv) growth under aerobic and anaerobic conditions, and (v) a large temperature range (5-75°C). It appears that only the temperature has a major influence, with an energy of activation of 69 kJ/mol. Different electron donors or electron acceptors only show a very minor influence on mE. On the basis of the data set, temperature correlations of mE have been derived for aerobic and anaerobic growth. The generalized concept for maintenance Gibbs energy is used to establish a correlation which allows the estimation of the biomass yield on electron donor as a function of C-source, electron donor, electron acceptor, N source, growth rate, and temperature. The advantage of using the mE parameter over other maintenance-related parameters (like μe, mO2, mD, γDmD) is discussed. © 1993 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260420415
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  • 8
    Digitale Medien
    Digitale Medien
    Solids retention time in spherical biofilms in a biofilm airlift suspension reactor (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 867-879 
    Details
    ISSN: 0006-3592
    Schlagwort(e): biofilm ; microbeads ; solids retention time ; airlift reactor ; particulates ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Fluorescent microparticles were used as tracer beads to measure the dynamics of solids in spherical biofilms in a biofilm airlift suspension reactor. Attachment to, release from, and penetration into the biofilms of the tracer beads were measured. The coverage of the biofilm surface was low and the steady state particle concentration on the surface was dependent on the biofilm surface characteristics. The measured attachment rate constant was identical in both experiments and appeared to be determined by the hydrodynamic conditions in the turbulent reactor. The attachment rate was much faster than the release rate of the tracer beads and, therefore, the solidsretention time in the biofilm particle is not due to a simple reversible adsorption-desorption process. The heterogeneity of the distribution oftracer beads on different sectors on the biofilm surface decreased duringthe attachment period. Due to random detachment processes the heterogeneity of the tracer bead distribution increased during the release periodThe tracer beads quickly penetrated into the biofilm and became distributed throughout the active layer of the biofilm. The observed penetration into biofilms, the nonuniform distribution on the biofilm surface, and the fast uptake and slow release of tracer beads cannot be described by a simple model based on a reversible adsorption-desorption mechanism, nor withexisting biofilm models. These biofilm models, which balance growth and advection assuming a uniform biofilm with a homogeneous surface, are inadequate for the description of the observed solids retention time in biofilms. Therefore, a new concept of biofilm dynamics is proposed, in which formation of cracks and fissures, which are rapidly filled with growing biomass, combined with nonuniform local detachment, explains the observed fast penetration into the biofilm of tracer beads, the long residence time, and the nonuniform distibution of fluorescent microparticles. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260440802
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  • 9
    Digitale Medien
    Digitale Medien
    Formation and growth of heterotrophic aerobic biofilms on small suspended particles in airlift reactors (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 595-608 
    Details
    ISSN: 0006-3592
    Schlagwort(e): biofilm ; aerobic waste water treatment ; airlift reactor ; waste water ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In this article, the conditions for aerobic biofilm formation on suspended particles, the dynamics of biofilm formation, and the biomass production during the start-up of a Biofilm Airlift Suspension reactor (BAS reactor) have been studied. The dynamics of biofilm formation during start up in the biofilm airlift suspension reactor follows three consecutive stages: bare carrier, microcolonies or patchy biofilms on the carrier, and biofilms completely covering the carrier. The effect of hydraulic retention time and of substrate loading rate on the formation of biofilms were investigated. To obtain in a BAS reactor a high biomass concentration and predominantly continuous biofilms, which completely surround the carrier, the hydraulic retention time must be shorter than the inverse of the maximum growth rate of the suspended bacteria. At longer hydraulic retention times, a low amount of attached biomass can be present on the carrier material as patchy biofilms. During the start-up at short hydraulic retention times the bare carrier concentration decreases, the amount of biomass per biofilm particle remains constant, and biomass increase in the reactor is due to increasing numbers of biofilm particles. The substrate surface loading rate has effect only on the amount of biomass on the biofilm particle. A higher surface load leads to a thicker biofilm.A strong nonlinear increase of the concentration of attached biomass in time was observed. This can be explained by a decreased abrasion of the biofilm particles due to the decreasing concentration of bare carriers. The detachment rate per biofilm area during the start-up is independent of the substrate loading rate, but depends strongly upon the bare carrier concentration.The Pirt-maintenance concept is applicable to BAS reactors. Surplus biomass production is diminished at high biomass concentrations. The average maximal yield of biomass on substrate during the experiments presented in this article was 0.44 ± 0.08 C-mol/C-mol, the maintenance value 0.019 ± 0.012 C-mol/(C-mol h). The lowest actual biomass yield measured in this study was 0.15 C-mol/C-mol. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260440506
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  • 10
    Digitale Medien
    Digitale Medien
    Stoichiometric model of the aerobic metabolism of the biological phosphorus removal process (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 837-848 
    Details
    ISSN: 0006-3592
    Schlagwort(e): phosphorus removal ; metabolic models ; stoichiometry ; polyphosphate ; poly-β-hydroxybutyrate ; glycogen ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In the aerobic phase of the biological phosphorus removal process, poly-β-hydroxybutyrate, produced during anaerobic conditions, is used for cell growth, phosphate uptake, and glycogen formation. A metabolic model of this process has been developed. The yields for growth, polyphosphate and glycogen formation are quantified using the coupling of all these conversions to the oxygen consumption. The uptake of phosphate and storage as polyphosphate is shown to have a direct effect on the observed oxygen consumption in the aerobic phase. The overall energy requirements for the P-metabolism are substantial: 25% of the acetate consumed during anaerobic conditions and 60% of the oxygen consumptions is used for the synthesis of polyphosphate and glycogen. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260440709
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