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M C M Van Loosdrecht - One of the best experts on this subject based on the ideXlab platform.
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effect of Dissolved Oxygen Concentration on sludge settleability
Applied Microbiology and Biotechnology, 2003Co-Authors: Antonio M P Martins, J J Heijnen, M C M Van LoosdrechtAbstract:This laboratory study presents a detailed evaluation of the effects of Dissolved Oxygen Concentration and accumulation of storage polymers on sludge settleability in activated sludge systems with an aerobic selector. The Oxygen and substrate availability regime were simulated in laboratory sequencing batch reactor systems. The experiments showed that low Dissolved Oxygen Concentration (≤1.1 mg O2 l−1) had a strong negative effect on sludge settleability, leading to the proliferation of filamentous bacteria (Thiothrix spp., Type 021N and Type 1851). This negative effect was stronger at high chemical Oxygen demand loading rate. This indicates that a compartmentalised (plug flow) aerobic contact tank, designed at short hydraulic residence time to guarantee a strong substrate gradient, with low Dissolved Oxygen Concentration, might be worse for sludge settleability than an "overdesigned" completely mixed contact tank. Contrary to the general hypothesis, the maximum specific acetate uptake rate, poly-β-hydroxybutyrate production rate, and resistance to short starvation periods are similar in both poor- and well-settling sludge. The results of this study support our previous hypothesis on the importance of substrate gradients for the development of filamentous structures in biological flocs, from soluble organic substrate gradients to Dissolved Oxygen gradients in sludge flocs.
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Effect of Dissolved Oxygen Concentration on sludge settleability.
Applied microbiology and biotechnology, 2003Co-Authors: Antonio M P Martins, J J Heijnen, M C M Van LoosdrechtAbstract:This laboratory study presents a detailed evaluation of the effects of Dissolved Oxygen Concentration and accumulation of storage polymers on sludge settleability in activated sludge systems with an aerobic selector. The Oxygen and substrate availability regime were simulated in laboratory sequencing batch reactor systems. The experiments showed that low Dissolved Oxygen Concentration (< or =1.1 mg O2 l(-1)) had a strong negative effect on sludge settleability, leading to the proliferation of filamentous bacteria (Thiothrix spp., Type 021N and Type 1851). This negative effect was stronger at high chemical Oxygen demand loading rate. This indicates that a compartmentalised (plug flow) aerobic contact tank, designed at short hydraulic residence time to guarantee a strong substrate gradient, with low Dissolved Oxygen Concentration, might be worse for sludge settleability than an "overdesigned" completely mixed contact tank. Contrary to the general hypothesis, the maximum specific acetate uptake rate, poly-beta-hydroxybutyrate production rate, and resistance to short starvation periods are similar in both poor- and well-settling sludge. The results of this study support our previous hypothesis on the importance of substrate gradients for the development of filamentous structures in biological flocs, from soluble organic substrate gradients to Dissolved Oxygen gradients in sludge flocs.
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influence of Dissolved Oxygen Concentration on nitrite accumulation in a biofilm airlift suspension reactor
Biotechnology and Bioengineering, 1997Co-Authors: J M Garrido, M C M Van Loosdrecht, W A J Van Benthum, J J HeijnenAbstract: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.
J J Heijnen - One of the best experts on this subject based on the ideXlab platform.
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effect of Dissolved Oxygen Concentration on sludge settleability
Applied Microbiology and Biotechnology, 2003Co-Authors: Antonio M P Martins, J J Heijnen, M C M Van LoosdrechtAbstract:This laboratory study presents a detailed evaluation of the effects of Dissolved Oxygen Concentration and accumulation of storage polymers on sludge settleability in activated sludge systems with an aerobic selector. The Oxygen and substrate availability regime were simulated in laboratory sequencing batch reactor systems. The experiments showed that low Dissolved Oxygen Concentration (≤1.1 mg O2 l−1) had a strong negative effect on sludge settleability, leading to the proliferation of filamentous bacteria (Thiothrix spp., Type 021N and Type 1851). This negative effect was stronger at high chemical Oxygen demand loading rate. This indicates that a compartmentalised (plug flow) aerobic contact tank, designed at short hydraulic residence time to guarantee a strong substrate gradient, with low Dissolved Oxygen Concentration, might be worse for sludge settleability than an "overdesigned" completely mixed contact tank. Contrary to the general hypothesis, the maximum specific acetate uptake rate, poly-β-hydroxybutyrate production rate, and resistance to short starvation periods are similar in both poor- and well-settling sludge. The results of this study support our previous hypothesis on the importance of substrate gradients for the development of filamentous structures in biological flocs, from soluble organic substrate gradients to Dissolved Oxygen gradients in sludge flocs.
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Effect of Dissolved Oxygen Concentration on sludge settleability.
Applied microbiology and biotechnology, 2003Co-Authors: Antonio M P Martins, J J Heijnen, M C M Van LoosdrechtAbstract:This laboratory study presents a detailed evaluation of the effects of Dissolved Oxygen Concentration and accumulation of storage polymers on sludge settleability in activated sludge systems with an aerobic selector. The Oxygen and substrate availability regime were simulated in laboratory sequencing batch reactor systems. The experiments showed that low Dissolved Oxygen Concentration (< or =1.1 mg O2 l(-1)) had a strong negative effect on sludge settleability, leading to the proliferation of filamentous bacteria (Thiothrix spp., Type 021N and Type 1851). This negative effect was stronger at high chemical Oxygen demand loading rate. This indicates that a compartmentalised (plug flow) aerobic contact tank, designed at short hydraulic residence time to guarantee a strong substrate gradient, with low Dissolved Oxygen Concentration, might be worse for sludge settleability than an "overdesigned" completely mixed contact tank. Contrary to the general hypothesis, the maximum specific acetate uptake rate, poly-beta-hydroxybutyrate production rate, and resistance to short starvation periods are similar in both poor- and well-settling sludge. The results of this study support our previous hypothesis on the importance of substrate gradients for the development of filamentous structures in biological flocs, from soluble organic substrate gradients to Dissolved Oxygen gradients in sludge flocs.
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influence of Dissolved Oxygen Concentration on nitrite accumulation in a biofilm airlift suspension reactor
Biotechnology and Bioengineering, 1997Co-Authors: J M Garrido, M C M Van Loosdrecht, W A J Van Benthum, J J HeijnenAbstract: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.
Antonio M P Martins - One of the best experts on this subject based on the ideXlab platform.
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effect of Dissolved Oxygen Concentration on sludge settleability
Applied Microbiology and Biotechnology, 2003Co-Authors: Antonio M P Martins, J J Heijnen, M C M Van LoosdrechtAbstract:This laboratory study presents a detailed evaluation of the effects of Dissolved Oxygen Concentration and accumulation of storage polymers on sludge settleability in activated sludge systems with an aerobic selector. The Oxygen and substrate availability regime were simulated in laboratory sequencing batch reactor systems. The experiments showed that low Dissolved Oxygen Concentration (≤1.1 mg O2 l−1) had a strong negative effect on sludge settleability, leading to the proliferation of filamentous bacteria (Thiothrix spp., Type 021N and Type 1851). This negative effect was stronger at high chemical Oxygen demand loading rate. This indicates that a compartmentalised (plug flow) aerobic contact tank, designed at short hydraulic residence time to guarantee a strong substrate gradient, with low Dissolved Oxygen Concentration, might be worse for sludge settleability than an "overdesigned" completely mixed contact tank. Contrary to the general hypothesis, the maximum specific acetate uptake rate, poly-β-hydroxybutyrate production rate, and resistance to short starvation periods are similar in both poor- and well-settling sludge. The results of this study support our previous hypothesis on the importance of substrate gradients for the development of filamentous structures in biological flocs, from soluble organic substrate gradients to Dissolved Oxygen gradients in sludge flocs.
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Effect of Dissolved Oxygen Concentration on sludge settleability.
Applied microbiology and biotechnology, 2003Co-Authors: Antonio M P Martins, J J Heijnen, M C M Van LoosdrechtAbstract:This laboratory study presents a detailed evaluation of the effects of Dissolved Oxygen Concentration and accumulation of storage polymers on sludge settleability in activated sludge systems with an aerobic selector. The Oxygen and substrate availability regime were simulated in laboratory sequencing batch reactor systems. The experiments showed that low Dissolved Oxygen Concentration (< or =1.1 mg O2 l(-1)) had a strong negative effect on sludge settleability, leading to the proliferation of filamentous bacteria (Thiothrix spp., Type 021N and Type 1851). This negative effect was stronger at high chemical Oxygen demand loading rate. This indicates that a compartmentalised (plug flow) aerobic contact tank, designed at short hydraulic residence time to guarantee a strong substrate gradient, with low Dissolved Oxygen Concentration, might be worse for sludge settleability than an "overdesigned" completely mixed contact tank. Contrary to the general hypothesis, the maximum specific acetate uptake rate, poly-beta-hydroxybutyrate production rate, and resistance to short starvation periods are similar in both poor- and well-settling sludge. The results of this study support our previous hypothesis on the importance of substrate gradients for the development of filamentous structures in biological flocs, from soluble organic substrate gradients to Dissolved Oxygen gradients in sludge flocs.
Athanassios Sambanis - One of the best experts on this subject based on the ideXlab platform.
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dual perfluorocarbon method to noninvasively monitor Dissolved Oxygen Concentration in tissue engineered constructs in vitro and in vivo
Biotechnology Progress, 2011Co-Authors: Robert C Long, Nicholas E Simpson, Athanassios SambanisAbstract:Noninvasive in vivo monitoring of tissue implants provides important correlations between construct function and the observed physiologic effects. As Oxygen is a key parameter affecting cell and tissue function, we established a monitoring method that utilizes 19F nuclear magnetic resonance (NMR) spectroscopy, with perfluorocarbons (PFCs) as Oxygen Concentration markers, to noninvasively monitor Dissolved Oxygen Concentration (DO) in tissue engineered implants. Specifically, we developed a dual PFC method capable of simultaneously measuring DO within a tissue construct and its surrounding environment, as the latter varies among animals and with physiologic conditions. In vitro studies using an NMR-compatible bioreactor demonstrated the feasibility of this method to monitor the DO within alginate beads containing metabolically active murine insulinoma βTC-tet cells, relative to the DO in the culture medium, under perfusion and static conditions. The DO profiles obtained under static conditions were supported by mathematical simulations of the system. In vivo, the dual PFC method was successful in tracking the Oxygenation state of entrapped βTC-tet cells and the surrounding peritoneal DO over 16 days in normal mice. DO measurements correlated well with the extent of cell growth and host cell attachment examined postexplantation. The peritoneal Oxygen environment was found to be variable and hypoxic, and significantly lower in the presence of metabolically active cells. The significance of the dual PFC system in providing critical DO measurements for entrapped cells and other tissue constructs, in vitro and in vivo, is discussed. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011
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in vivo noninvasive monitoring of Dissolved Oxygen Concentration within an implanted tissue engineered pancreatic construct
Tissue Engineering Part C-methods, 2011Co-Authors: Athanassios SambanisAbstract:The function of an implanted tissue-engineered pancreatic construct is influenced by many in vivo factors; however, assessing its function is based primarily on end physiologic effects. As Oxygen significantly affects cell function, we established a dual perfluorocarbon method that utilizes 19F nuclear magnetic resonance spectroscopy, with perfluorocarbons as Oxygen Concentration markers, to noninvasively monitor Dissolved Oxygen Concentration (DO) in βTC-tet cell-containing alginate beads and at the implantation milieu. Beads were implanted in the peritoneal cavity of normal and streptozotocin-induced diabetic mice. Using this method, the feasibility of acquiring real-time in vivo DO measurements was demonstrated. Results showed that the mouse peritoneal environment is hypoxic and the DO is further reduced when βTC-tet cell constructs were implanted. The DO within cell-containing beads decreased considerably over time and could be correlated with the relative changes in the number of viable encapsulated ...
Scott Anderson - One of the best experts on this subject based on the ideXlab platform.
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effects of ambient and Dissolved Oxygen Concentration in ultrapure water on initial growth of native oxide on a silicon 100 surface
Journal of The Electrochemical Society, 2005Co-Authors: Fuhe Li, Marjorie K Balazs, Scott AndersonAbstract:The effects of ambient and Dissolved Oxygen Concentration in ultrapure water (UPW) on native oxide growth were studied at room temperature using a silicon (100) surface. Studies focused on the initial stage of the surfaceoxidation immediately after the HF cleaning. The silicon surfaces were exposed at a fixed duration to the UPW with different Dissolved Oxygen Concentrations, open air, and dry nitrogen, respectively. The SiO 2 equivalent thicknesses of the native oxides formed were then measured and compared. Results indicate that the ambient and the Dissolved Oxygen Concentration in UPW dramatically affect the growth rate of the native oxide. Decreasing the Dissolved Oxygen Concentration in UPW and using an inert and dry atmosphere for the ultracleaning is shown to reduce or eventually prevent the native oxide from growing on silicon surfaces. The SiO 2 equivalent thicknesses of the native oxide formed on these surfaces were characterized by a rapid acid extraction followed by a determination for extractable silicon. The extractable silicon was determined by a high-resolution magnetic-sector ICP mass spectrometer. This analytical method has been demonstrated for measurement of an oxide thickness on a silicon wafer surface down to a monolayer range with a possible 0.1 A resolution.