The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Mark 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, Joseph J. Heijnen, Mark 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, Joseph J. Heijnen, Mark 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.
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, Joseph J. Heijnen, Mark 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, Joseph J. Heijnen, Mark 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.
Joseph 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, Joseph J. Heijnen, Mark 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, Joseph J. Heijnen, Mark 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.
Jun Deng - One of the best experts on this subject based on the ideXlab platform.
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Effect of Oxygen Concentration on low-temperature exothermic oxidation of pulverized coal
Thermochimica Acta, 2018Co-Authors: Jun Deng, Ren Lifeng, Changkui Lei, Gaoming Wei, Wei-feng WangAbstract:Abstract Low-temperature exothermic oxidation characteristics of pulverized sub-bituminous coal was investigated using differential scanning calorimetry system in atmospheres where the Oxygen Concentrations were 21, 17, 13, 9, and 5 vol. %, respectively. The results indicate that the heat flow gradually decreases after it reaches the maximum value. A decreased Oxygen Concentration had a delaying effect on the heat flow and derivative of heat flow curves. A low Oxygen Concentration has typical stage characteristics for inhibiting the exothermic oxidation of pulverized coal. The Oxygen Concentration has a significant influence on the kinetics characteristics and kinetics parameters. The apparent activation energy increased under different Oxygen Concentrations with an increase in the conversion rate. The apparent activation energy was less than that in the low Oxygen Concentration under a high Oxygen Concentration. When the Oxygen Concentration less than 9%, the activation energy increases significantly.
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The effect of Oxygen Concentration on the non-isothermal combustion of coal
Thermochimica Acta, 2017Co-Authors: Jun Deng, Yang Xiao, Hu WenAbstract:Abstract By thermogravimetric experiments under various Oxygen Concentrations, Oxygen-adsorption mass-gain and decomposition/combustion mass-loss stages of coal combustion were investigated. Apparent activation energies were calculated by Starink equation. The results indicate that mass change through Oxygen-adsorption mass-gain stage to decomposition/combustion mass-loss stage consists of adsorption mass gain, oxidation/decomposition mass loss, and combustion mass loss. Combustion contributes more to mass loss than do oxidation/decomposition. Inhibition of Oxygen Concentration in thermal curves shows a linear relationship with Oxygen Concentration. Different characteristic temperatures show different variations towards Oxygen Concentrations. At Oxygen-adsorption mass-gain stage, apparent activation energy increases with the conversion rate, however, the variations caused by Oxygen Concentrations were different for different coals. Apparent activation energy first increases and then decreases at decomposition/combustion mass-loss stage whereas it decreases with decreasing Oxygen Concentration. The conversion rate when the apparent energy reached the maximum increases with increasing Oxygen Concentration, but the corresponding temperature has little change.
Sergei Savikhin - One of the best experts on this subject based on the ideXlab platform.
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Oxygen Concentration Inside a Functioning Photosynthetic Cell
Biophysical journal, 2014Co-Authors: Shigeharu Kihara, Daniel A. Hartzler, Sergei SavikhinAbstract:The excess Oxygen Concentration in the photosynthetic membranes of functioning Oxygenic photosynthetic cells was estimated using classical diffusion theory combined with experimental data on Oxygen production rates of cyanobacterial cells. The excess Oxygen Concentration within the plesiomorphic cyanobacterium Gloeobactor violaceus is only 0.025 μM, or four orders of magnitude lower than the Oxygen Concentration in air-saturated water. Such a low Concentration suggests that the first Oxygenic photosynthetic bacteria in solitary form could have evolved ∼2.8 billion years ago without special mechanisms to protect them against reactive Oxygen species. These mechanisms instead could have been developed during the following ∼500 million years while the Oxygen level in the Earth’s atmosphere was slowly rising. Excess Oxygen Concentrations within individual cells of the apomorphic cyanobacteria Synechocystis and Synechococcus are 0.064 and 0.25 μM, respectively. These numbers suggest that intramembrane and intracellular proteins in isolated Oxygenic photosynthetic cells are not subjected to excessively high Oxygen levels. The situation is different for closely packed colonies of photosynthetic cells. Calculations show that the excess Concentration within colonies that are ∼40 μm or larger in diameter can be comparable to the Oxygen Concentration in air-saturated water, suggesting that species forming colonies require protection against reactive Oxygen species even in the absence of Oxygen in the surrounding atmosphere.
