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  • 1970-1974  (8)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 15 (1973), S. 933-949 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The response of aerobically growing heterogeneous microbial populations of sewage origin to step increases and decreases in pH were studied in both once-through and cell recycle systems. The pH range studied was 2.7 to 8.0. All studies were conducted at a dilution rate of 0.125 hr-1, and all shocks were administered from a base or preshock pH level of 6.4 to 6.7. In each experiment, the preshock or initial “steady state” was assessed, the pH of the feed changed, and the resulting transient behavior of the system examined until attainment of the new or final “steady state” was approached. The major objectives of the work were to characterize the nature of the response with respect to biomass and effluent substrate concentrations, types of microbial populations present and chemical composition of the biomass, and to obtain guidelines as to allowable change in pH in waste streams. It was found in once-through systems that substrate removal efficiency recovered from pH levels as low as 3.0 after rather long periods of transient leakage of substrate. Cell recycle attenuated the severity of substrate leakage. In all cases of severe acid shock, the microbial population changed from predominantly bacterial-protozoan to one consisting predominantly of filamentous fungi. Changes in chemical composition of the sludge (protein and carbohydrate content) were consistent with the population changes. Based upon the results, it can be conservatively estimated that changes in pH of no more than one unit from the neutral preshock range can be tolerated without possible disruption of biochemical efficiency of substrate removal.
    Additional Material: 10 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 15 (1973), S. 589-596 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 16 (1974), S. 723-738 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Previous experimentation in our laboratory has shown that the classical theory developed for continuous growth of pure cultures in completely mixed aerobic systems in which the recycle cell concentration factor, c (where c = XR/X), is a selectable system constant, did not provide a suitable model for the heterogeneous (natural) populations of the activated sludge process. Another model was derived in which the recycle cell concentration, XR was employed as a system constant instead of c, and computational analysis was performed. Laboratory pilot plant experimentation was undertaken in order to determine whether a “steady state” in aerator biological solids concentration, X̄, and substrate concentration, S̄, could be approached under this mode of operation. Studies were performed at various organic feed concentrations holding dilution rate, D, at 0.125 hr-1, hydraulic recycle ratio, α, at 0.25, and XR at 10,000 mg/liter. Also, values of maximum specific growth rate, μmax, and saturation constant, Ks were determined. It was found that the model approached the steady state condition with heterogeneous populations more closely than did the classical model, and the high degree of treatment efficiency predicted by the model was demonstrated experimentally.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 13 (1971), S. 125-145 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In a previous report it was concluded that steady-state operation of completely mixed reactors for growth of heterogeneous microbial populations, i.e., activated sludge processes, was extremely difficult to attain if maintenance of a constant sludge recycle ratio, c, was required, and equations were devised in which the concentration of cells in the recycle, xR, rather than the recycle ratio, was constant. In this report the equations are developed and computational analysis shows the effect on substrate and cell concentrations in the reactor of operational variables such as inflowing feed concentration, hydraulic recycle ratio, recycle sludge concentration, dilution rate, and the biological “constants” μm, ks, and Y. The stabilizing effect of operating with constant xR on the dilute-out pattern is shown.
    Additional Material: 11 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 13 (1971), S. 113-123 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Values of cell yield collected over a period of eight years for heterogeneous populations of sewage origin acclimated to glucose in both batch and continuous culture were subjected to statistical analysis. The cell yield for this sole source of carbon (glucose) ranged from 36 to 88 per cent in batch culture, and 32 to 69 per cent in continuous culture. Because experimental conditions were known and well defined, the variability in cell yield is attributable to the ecological variation inherent in a heterogeneous population. The data presented demonstrate the futility of attempts to define Y for such populations as a precise theoretical constant dependent upon thermodynamic properties of the substrate.
    Additional Material: 3 Ill.
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  • 6
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Nitrifying characteristics were compared for an extended aeration (total cell recycle) process and one employing an engineering modification of the process utilizing a “hydrolytic assist” to aid biological autodigestion. Laboratory pilot plants were run over a period of years, and it was found that the recently recommended “hydrolytic assist” did not militate against production of a highly nitrified effluent. Under this mode of operation, the effluent was as nitrified as the effluent from the normal extended aeration process. It was also found that the modified process rapidly recovered its nitrifying capability after a period of deprivation of excess ammonia nitrogen. Throughout the period of operation, substrate removal efficiency remained high.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 16 (1974), S. 423-427 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 12 (1970), S. 519-539 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The mechanisms and kinetic course of BOD exertion were compared in both open and closed systems. Two open reactors, a simulated stream device, and an open stirred reactor were employed, and the closed systems consisted of standard BOD bottles and 2.4-liter vessels. In the closed systems, both quiescent and stirred conditions of incubation were examined. Biological solids concentration, bacteria and protozoa concentration, substrate analysis, and chemical oxygen demand as well as biochemical oxygen utilization were employed to assess the performance of these systems.Oxygen uptake rate constants were observed to increase with increasing concentration o carbon source, thus militating against irect use of the usual dilution technique for predicting rate of deoxygenation in receiving streams. The relationship between specific O2 uptake rate and substrate concentration approximated a hyperbolic function similar to the Mono relationship for specific growth rate and substrate concentration. A technique using an open stirred reactor than the standard BOD bottle dilution technique is recommended.
    Additional Material: 8 Ill.
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