The Experts below are selected from a list of 17916 Experts worldwide ranked by ideXlab platform
Bruce E Rittmann - One of the best experts on this subject based on the ideXlab platform.
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nitrite accumulation from simultaneous free ammonia and free nitrous acid inhibition and Oxygen Limitation in a continuous flow biofilm reactor
Biotechnology and Bioengineering, 2015Co-Authors: Seongjun Park, Jin Wook Chung, Bruce E Rittmann, Wookeun BaeAbstract:To achieve nitrite accumulation for shortcut biological nitrogen removal (SBNR) in a biofilm process, we explored the simultaneous effects of Oxygen Limitation and free ammonia (FA) and free nitrous acid (FNA) inhibition in the nitrifying biofilm. We used the multi-species nitrifying biofilm model (MSNBM) to identify conditions that should or should not lead to nitrite accumulation, and evaluated the effectiveness of those conditions with experiments in continuous flow biofilm reactors (CFBRs). CFBR experiments were organized into four sets with these expected outcomes based on the MSNBM as follows: (i) Control, giving full nitrification; (ii) Oxygen Limitation, giving modest long-term nitrite build up; (iii) FA inhibition, giving no long-term nitrite accumulation; and (iv) FA inhibition plus Oxygen Limitation, giving major long-term nitrite accumulation. Consistent with MSNBM predictions, the experimental results showed that nitrite accumulated in sets 2-4 in the short term, but long-term nitrite accumulation was maintained only in sets 2 and 4, which involved Oxygen Limitation. Furthermore, nitrite accumulation was substantially greater in set 4, which also included FA inhibition. However, FA inhibition (and accompanying FNA inhibition) alone in set 3 did not maintained long-term nitrite accumulation. Nitrite-oxidizing bacteria (NOB) activity batch tests confirmed that little NOB or only a small fraction of NOB were present in the biofilms for sets 4 and 2, respectively. The experimental data supported the previous modeling results that nitrite accumulation could be achieved with a lower ammonium concentration than had been required for a suspended-growth process. Additional findings were that the biofilm exposed to low dissolved Oxygen (DO) Limitation and FA inhibition was substantially denser and probably had a lower detachment rate.
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nitrite accumulation from simultaneous free ammonia and free nitrous acid inhibition and Oxygen Limitation in a continuous flow biofilm reactor
Biotechnology and Bioengineering, 2015Co-Authors: Seongjun Park, Jin Wook Chung, Bruce E RittmannAbstract:To achieve nitrite accumulation for shortcut biological nitrogen removal (SBNR) in a biofilm process, we explored the simultaneous effects of Oxygen Limitation and free ammonia (FA) and free nitrous acid (FNA) inhibition in the nitrifying biofilm. We used the multi-species nitrifying biofilm model (MSNBM) to identify conditions that should or should not lead to nitrite accumulation, and evaluated the effectiveness of those conditions with experiments in continuous flow biofilm reactors (CFBRs). CFBR experiments were organized into four sets with these expected outcomes based on the MSNBM as follows: (i) Control, giving full nitrification; (ii) Oxygen Limitation, giving modest long-term nitrite build up; (iii) FA inhibition, giving no long-term nitrite accumulation; and (iv) FA inhibition plus Oxygen Limitation, giving major long-term nitrite accumulation. Consistent with MSNBM predictions, the experimental results showed that nitrite accumulated in sets 2–4 in the short term, but long-term nitrite accumulation was maintained only in sets 2 and 4, which involved Oxygen Limitation. Furthermore, nitrite accumulation was substantially greater in set 4, which also included FA inhibition. However, FA inhibition (and accompanying FNA inhibition) alone in set 3 did not maintained long-term nitrite accumulation. Nitrite-oxidizing bacteria (NOB) activity batch tests confirmed that little NOB or only a small fraction of NOB were present in the biofilms for sets 4 and 2, respectively. The experimental data supported the previous modeling results that nitrite accumulation could be achieved with a lower ammonium concentration than had been required for a suspended-growth process. Additional findings were that the biofilm exposed to low dissolved Oxygen (DO) Limitation and FA inhibition was substantially denser and probably had a lower detachment rate. Biotechnol. Bioeng. 2015;112: 43–52. © 2014 Wiley Periodicals, Inc.
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multi species nitrifying biofilm model msnbm including free ammonia and free nitrous acid inhibition and Oxygen Limitation
Biotechnology and Bioengineering, 2010Co-Authors: Seongjun Park, Wookeun Bae, Bruce E RittmannAbstract:A multi-species nitrifying biofilm model (MSNBM) is developed to describe nitrite accumulation by simultaneous free ammonia (FA) and free nitrous acid (FNA) inhibition, direct pH inhibition, and Oxygen Limitation in a biofilm. The MSNBM addresses the spatial gradient of pH with biofilm depth and how it induces changes of FA and FNA speciation and inhibition. Simulations using the MSNBM in a completely mixed biofilm reactor show that influent total ammonia nitrogen (TAN) concentration, bulk dissolved Oxygen (DO) concentration, and buffer concentration exert significant control on the suppression of nitrite-oxidizing bacteria (NOB) and shortcut biological nitrogen removal (SBNR), but the pH in the bulk liquid has a weaker influence. Ammonium oxidation increases the nitrite concentration and decreases the pH, which together can increase FNA inhibition of NOB in the biofilm. Thus, a low buffer concentration can accentuate SBNR. DO and influent TAN concentrations are efficient means to enhance DO Limitation, which affects NOB more than ammonia-oxidizing bacteria (AOB) inside the biofilm. With high influent TAN concentration, FA inhibition is dominant at an early phase, but finally DO Limitation becomes more important as TAN degradation and biofilm growth proceed. MSNBM results indicate that Oxygen depletion and FNA inhibition throughout the biofilm continuously suppress the growth of NOB, which helps achieve SBNR with a lower TAN concentration than in systems without concentration gradients.
Seongjun Park - One of the best experts on this subject based on the ideXlab platform.
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nitrite accumulation from simultaneous free ammonia and free nitrous acid inhibition and Oxygen Limitation in a continuous flow biofilm reactor
Biotechnology and Bioengineering, 2015Co-Authors: Seongjun Park, Jin Wook Chung, Bruce E Rittmann, Wookeun BaeAbstract:To achieve nitrite accumulation for shortcut biological nitrogen removal (SBNR) in a biofilm process, we explored the simultaneous effects of Oxygen Limitation and free ammonia (FA) and free nitrous acid (FNA) inhibition in the nitrifying biofilm. We used the multi-species nitrifying biofilm model (MSNBM) to identify conditions that should or should not lead to nitrite accumulation, and evaluated the effectiveness of those conditions with experiments in continuous flow biofilm reactors (CFBRs). CFBR experiments were organized into four sets with these expected outcomes based on the MSNBM as follows: (i) Control, giving full nitrification; (ii) Oxygen Limitation, giving modest long-term nitrite build up; (iii) FA inhibition, giving no long-term nitrite accumulation; and (iv) FA inhibition plus Oxygen Limitation, giving major long-term nitrite accumulation. Consistent with MSNBM predictions, the experimental results showed that nitrite accumulated in sets 2-4 in the short term, but long-term nitrite accumulation was maintained only in sets 2 and 4, which involved Oxygen Limitation. Furthermore, nitrite accumulation was substantially greater in set 4, which also included FA inhibition. However, FA inhibition (and accompanying FNA inhibition) alone in set 3 did not maintained long-term nitrite accumulation. Nitrite-oxidizing bacteria (NOB) activity batch tests confirmed that little NOB or only a small fraction of NOB were present in the biofilms for sets 4 and 2, respectively. The experimental data supported the previous modeling results that nitrite accumulation could be achieved with a lower ammonium concentration than had been required for a suspended-growth process. Additional findings were that the biofilm exposed to low dissolved Oxygen (DO) Limitation and FA inhibition was substantially denser and probably had a lower detachment rate.
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nitrite accumulation from simultaneous free ammonia and free nitrous acid inhibition and Oxygen Limitation in a continuous flow biofilm reactor
Biotechnology and Bioengineering, 2015Co-Authors: Seongjun Park, Jin Wook Chung, Bruce E RittmannAbstract:To achieve nitrite accumulation for shortcut biological nitrogen removal (SBNR) in a biofilm process, we explored the simultaneous effects of Oxygen Limitation and free ammonia (FA) and free nitrous acid (FNA) inhibition in the nitrifying biofilm. We used the multi-species nitrifying biofilm model (MSNBM) to identify conditions that should or should not lead to nitrite accumulation, and evaluated the effectiveness of those conditions with experiments in continuous flow biofilm reactors (CFBRs). CFBR experiments were organized into four sets with these expected outcomes based on the MSNBM as follows: (i) Control, giving full nitrification; (ii) Oxygen Limitation, giving modest long-term nitrite build up; (iii) FA inhibition, giving no long-term nitrite accumulation; and (iv) FA inhibition plus Oxygen Limitation, giving major long-term nitrite accumulation. Consistent with MSNBM predictions, the experimental results showed that nitrite accumulated in sets 2–4 in the short term, but long-term nitrite accumulation was maintained only in sets 2 and 4, which involved Oxygen Limitation. Furthermore, nitrite accumulation was substantially greater in set 4, which also included FA inhibition. However, FA inhibition (and accompanying FNA inhibition) alone in set 3 did not maintained long-term nitrite accumulation. Nitrite-oxidizing bacteria (NOB) activity batch tests confirmed that little NOB or only a small fraction of NOB were present in the biofilms for sets 4 and 2, respectively. The experimental data supported the previous modeling results that nitrite accumulation could be achieved with a lower ammonium concentration than had been required for a suspended-growth process. Additional findings were that the biofilm exposed to low dissolved Oxygen (DO) Limitation and FA inhibition was substantially denser and probably had a lower detachment rate. Biotechnol. Bioeng. 2015;112: 43–52. © 2014 Wiley Periodicals, Inc.
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multi species nitrifying biofilm model msnbm including free ammonia and free nitrous acid inhibition and Oxygen Limitation
Biotechnology and Bioengineering, 2010Co-Authors: Seongjun Park, Wookeun Bae, Bruce E RittmannAbstract:A multi-species nitrifying biofilm model (MSNBM) is developed to describe nitrite accumulation by simultaneous free ammonia (FA) and free nitrous acid (FNA) inhibition, direct pH inhibition, and Oxygen Limitation in a biofilm. The MSNBM addresses the spatial gradient of pH with biofilm depth and how it induces changes of FA and FNA speciation and inhibition. Simulations using the MSNBM in a completely mixed biofilm reactor show that influent total ammonia nitrogen (TAN) concentration, bulk dissolved Oxygen (DO) concentration, and buffer concentration exert significant control on the suppression of nitrite-oxidizing bacteria (NOB) and shortcut biological nitrogen removal (SBNR), but the pH in the bulk liquid has a weaker influence. Ammonium oxidation increases the nitrite concentration and decreases the pH, which together can increase FNA inhibition of NOB in the biofilm. Thus, a low buffer concentration can accentuate SBNR. DO and influent TAN concentrations are efficient means to enhance DO Limitation, which affects NOB more than ammonia-oxidizing bacteria (AOB) inside the biofilm. With high influent TAN concentration, FA inhibition is dominant at an early phase, but finally DO Limitation becomes more important as TAN degradation and biofilm growth proceed. MSNBM results indicate that Oxygen depletion and FNA inhibition throughout the biofilm continuously suppress the growth of NOB, which helps achieve SBNR with a lower TAN concentration than in systems without concentration gradients.
Wilco C. E. P. Verberk - One of the best experts on this subject based on the ideXlab platform.
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Oxygen Limitation may affect the temperature and size dependence of metabolism in aquatic ectotherms
Proceedings of the National Academy of Sciences of the United States of America, 2020Co-Authors: Wilco C. E. P. Verberk, Juan G Rubalcaba, Jan A Hendriks, Bart Saris, Arthur H WoodsAbstract:Both Oxygen and temperature are fundamental factors determining metabolic performance, fitness, ecological niches, and responses of many aquatic organisms to climate change. Despite the importance of physical and physiological constraints on Oxygen supply affecting aerobic metabolism of aquatic ectotherms, ecological theories such as the metabolic theory of ecology have focused on the effects of temperature rather than Oxygen. This gap currently impedes mechanistic models from accurately predicting metabolic rates (i.e., Oxygen consumption rates) of aquatic organisms and restricts predictions to resting metabolism, which is less affected by Oxygen Limitation. Here, we expand on models of metabolic scaling by accounting for the role of Oxygen availability and temperature on both resting and active metabolic rates. Our model predicts that Oxygen Limitation is more likely to constrain metabolism in larger, warmer, and active fish. Consequently, active metabolic rates are less responsive to temperature than are resting metabolic rates, and metabolism scales to body size with a smaller exponent whenever temperatures or activity levels are higher. Results from a metaanalysis of fish metabolic rates are consistent with our model predictions. The observed interactive effects of temperature, Oxygen availability, and body size predict that global warming will limit the aerobic scope of aquatic ectotherms and may place a greater metabolic burden on larger individuals, impairing their physiological performance in the future. Our model reconciles the metabolic theory with empirical observations of Oxygen Limitation and provides a formal, quantitative framework for predicting both resting and active metabolic rate and hence aerobic scope of aquatic ectotherms.
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SYMPOSIUM AnaerobicMetabolism at Thermal Extremes: AMetabolomic Test of the Oxygen Limitation Hypothesis in an Aquatic Insect
2016Co-Authors: Wilco C. E. P. Verberk, U. Sommer, R. L. Davidson, M. R. ViantAbstract:Synopsis Thermal limits in ectotherms may arise through a mismatch between supply and demand of Oxygen. At higher temperatures, the ability of their cardiac and ventilatory activities to supply Oxygen becomes insufficient to meet their elevated Oxygen demand. Consequently, higher levels of Oxygen in the environment are predicted to enhance tolerance of heat, whereas reductions in Oxygen are expected to reduce thermal limits. Here, we extend previous research on thermal limits and Oxygen Limitation in aquatic insect larvae and directly test the hypothesis of increased anaerobic metabolism and lower energy status at thermal extremes. We quantified metabolite profiles in stonefly nymphs under varying tem-peratures and Oxygen levels. Under normoxia, the concept of Oxygen Limitation applies to the insects studied. Shifts in the metabolome of heat-stressed stonefly nymphs clearly indicate the onset of anaerobic metabolism (e.g., accumulation of lactate, acetate, and alanine), a perturbation of the tricarboxylic acid cycle (e.g., accumulation of succinate and malate), and a decrease in energy status (e.g., ATP), with corresponding decreases in their ability to survive heat stress. These shifts were more pronounced under hypoxic conditions, and negated by hyperoxia, which also improved heat tolerance. Perturbations of metabolic pathways in response to either heat stress or hypoxia were found to be somewhat similar but not identical. Under hypoxia, energy status was greatly compromised at thermal extremes, but energy shortage an
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anaerobic metabolism at thermal extremes a metabolomic test of the Oxygen Limitation hypothesis in an aquatic insect
Integrative and Comparative Biology, 2013Co-Authors: Wilco C. E. P. Verberk, Ulf Somme, Robe L Davidso, Mark R ViaAbstract:Thermal limits in ectotherms may arise through a mismatch between supply and demand of Oxygen. At higher temperatures, the ability of their cardiac and ventilatory activities to supply Oxygen becomes insufficient to meet their elevated Oxygen demand. Consequently, higher levels of Oxygen in the environment are predicted to enhance tolerance of heat, whereas reductions in Oxygen are expected to reduce thermal limits. Here, we extend previous research on thermal limits and Oxygen Limitation in aquatic insect larvae and directly test the hypothesis of increased anaerobic metabolism and lower energy status at thermal extremes. We quantified metabolite profiles in stonefly nymphs under varying temperatures and Oxygen levels. Under normoxia, the concept of Oxygen Limitation applies to the insects studied. Shifts in the metabolome of heat-stressed stonefly nymphs clearly indicate the onset of anaerobic metabolism (e.g., accumulation of lactate, acetate, and alanine), a perturbation of the tricarboxylic acid cycle (e.g., accumulation of succinate and malate), and a decrease in energy status (e.g., ATP), with corresponding decreases in their ability to survive heat stress. These shifts were more pronounced under hypoxic conditions, and negated by hyperoxia, which also improved heat tolerance. Perturbations of metabolic pathways in response to either heat stress or hypoxia were found to be somewhat similar but not identical. Under hypoxia, energy status was greatly compromised at thermal extremes, but energy shortage and anaerobic metabolism could not be conclusively identified as the sole cause underlying thermal limits under hyperoxia. Metabolomics proved useful for suggesting a range of possible mechanisms to explore in future investigations, such as the involvement of leaking membranes or free radicals. In doing so, metabolomics provided a more complete picture of changes in metabolism under hypoxia and heat stress.
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can Oxygen set thermal limits in an insect and drive gigantism
PLOS ONE, 2011Co-Authors: Wilco C. E. P. Verberk, David T BiltonAbstract:Background Thermal limits may arise through a mismatch between Oxygen supply and demand in a range of animal taxa. Whilst this Oxygen Limitation hypothesis is supported by data from a range of marine fish and invertebrates, its generality remains contentious. In particular, it is unclear whether Oxygen Limitation determines thermal extremes in tracheated arthropods, where Oxygen Limitation may be unlikely due to the efficiency and plasticity of tracheal systems in supplying Oxygen directly to metabolically active tissues. Although terrestrial taxa with open tracheal systems may not be prone to Oxygen Limitation, species may be affected during other life-history stages, particularly if these rely on diffusion into closed tracheal systems. Furthermore, a central role for Oxygen Limitation in insects is envisaged within a parallel line of research focussing on insect gigantism in the late Palaeozoic. Methodology/Principal Findings Here we examine thermal maxima in the aquatic life stages of an insect at normoxia, hypoxia (14 kPa) and hyperoxia (36 kPa). We demonstrate that upper thermal limits do indeed respond to external Oxygen supply in the aquatic life stages of the stonefly Dinocras cephalotes, suggesting that the critical thermal limits of such aquatic larvae are set by Oxygen Limitation. This could result from impeded Oxygen delivery, or limited Oxygen regulatory capacity, both of which have implications for our understanding of the limits to insect body size and how these are influenced by atmospheric Oxygen levels. Conclusions/Significance These findings extend the generality of the hypothesis of Oxygen Limitation of thermal tolerance, suggest that Oxygen constraints on body size may be stronger in aquatic environments, and that Oxygen toxicity may have actively selected for gigantism in the aquatic stages of Carboniferous arthropods.
Daniel Pauly - One of the best experts on this subject based on the ideXlab platform.
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the gill Oxygen Limitation theory golt and its critics
Science Advances, 2021Co-Authors: Daniel PaulyAbstract:The gill-Oxygen Limitation theory (GOLT) provides mechanisms for key aspects of the biology (food conversion efficiency, growth and its response to temperature, the timing of maturation, and others) of water-breathing ectotherms (WBEs). The GOLT's basic tenet is that the surface area of the gills or other respiratory surfaces of WBE cannot, as two-dimensional structures, supply them with sufficient Oxygen to keep up with the growth of their three-dimensional bodies. Thus, a lower relative Oxygen supply induces sexual maturation, and later a slowing and cessation of growth, along with an increase of physiological processes relying on glycolytic enzymes and a declining role of oxidative enzymes. Because the "dimensional tension" underlying this argument is widely misunderstood, emphasis is given to a detailed refutation of objections to the GOLT. This theory still needs to be put on a solid quantitative basis, which will occur after the misconceptions surrounding it are put to rest.
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The Relationship Between Size at Maturity and Maximum Size in Cichlid Populations Corroborates the Gill-Oxygen Limitation Theory (GOLT)
'Asian Fisheries Society', 2021Co-Authors: Upali S. Amarasinghe, Daniel PaulyAbstract:Fish generally mature at a smaller fraction of their maximum sizes than birds and mammals. The farmed tilapia (Family Cichlidae) can tolerate adverse conditions that result in stunting and which also cause the fish to spawn at small size. Such spawning at small size (or ‘early spawning’) is usually perceived as a unique feature of tilapia. The mechanism that explains how stressful environmental conditions tend to reduce the maximum size that fish can reach is very general and should apply to all fish. However, not all fish species are equally hardy, and most fish do not survive in the stunted or dwarf form under stressful environmental conditions. Tilapia, and other cichlids, on the other hand, can handle stressful conditions, if by remaining stunted. The present study shows that tilapia and other cichlids do not spawn ‘earlier’ than other teleosts. Rather, they are exceptionally tolerant of stressful environmental conditions, but with elevated metabolism. By reducing their growth and the maximum size they can reach ‘stunting’, they also reduce the sizes at which their maturity is initiated (‘early spawning’). This corroborates the gill-Oxygen Limitation theory (GOLT), which identifies spawning as an event rather than a determinant of fish growth
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a precis of gill Oxygen Limitation theory golt with some emphasis on the eastern mediterranean
Mediterranean Marine Science, 2019Co-Authors: Daniel PaulyAbstract:A summary of the Gill-Oxygen Limitation Theory (GOLT) is presented, i.e., of a theory seeking to explain a variety of life processes in fish and aquatic invertebrate by the fact that that the surface of their gills (and hence their Oxygen supply) cannot, as 2-dimensional objects, keep up with the growth of their 3-dimensional bodies, and thus with their Oxygen requirements. Various processes and attributes of fish and aquatic invertebrates are presented which had to date no mechanistic explanation, but which fit within the GOLT, offered here as a tool to interpret phenomena that until now were perceived as unrelated. However, the GOLT should also help to address practical problems, such as arise for fish farming when water temperature increases because of global warming.
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on confusing cause and effect in the Oxygen Limitation of fish
Global Change Biology, 2018Co-Authors: Daniel Pauly, William W L CheungAbstract:This letter deals with the critique by Lefevre, McKenzie, and Nilsson (2017, 2018) of the use of Gill-Oxygen Limitation Theory (GOLT) to explain observed and predict further decreases of the maximum body size of fish under warming.
Wookeun Bae - One of the best experts on this subject based on the ideXlab platform.
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nitrite accumulation from simultaneous free ammonia and free nitrous acid inhibition and Oxygen Limitation in a continuous flow biofilm reactor
Biotechnology and Bioengineering, 2015Co-Authors: Seongjun Park, Jin Wook Chung, Bruce E Rittmann, Wookeun BaeAbstract:To achieve nitrite accumulation for shortcut biological nitrogen removal (SBNR) in a biofilm process, we explored the simultaneous effects of Oxygen Limitation and free ammonia (FA) and free nitrous acid (FNA) inhibition in the nitrifying biofilm. We used the multi-species nitrifying biofilm model (MSNBM) to identify conditions that should or should not lead to nitrite accumulation, and evaluated the effectiveness of those conditions with experiments in continuous flow biofilm reactors (CFBRs). CFBR experiments were organized into four sets with these expected outcomes based on the MSNBM as follows: (i) Control, giving full nitrification; (ii) Oxygen Limitation, giving modest long-term nitrite build up; (iii) FA inhibition, giving no long-term nitrite accumulation; and (iv) FA inhibition plus Oxygen Limitation, giving major long-term nitrite accumulation. Consistent with MSNBM predictions, the experimental results showed that nitrite accumulated in sets 2-4 in the short term, but long-term nitrite accumulation was maintained only in sets 2 and 4, which involved Oxygen Limitation. Furthermore, nitrite accumulation was substantially greater in set 4, which also included FA inhibition. However, FA inhibition (and accompanying FNA inhibition) alone in set 3 did not maintained long-term nitrite accumulation. Nitrite-oxidizing bacteria (NOB) activity batch tests confirmed that little NOB or only a small fraction of NOB were present in the biofilms for sets 4 and 2, respectively. The experimental data supported the previous modeling results that nitrite accumulation could be achieved with a lower ammonium concentration than had been required for a suspended-growth process. Additional findings were that the biofilm exposed to low dissolved Oxygen (DO) Limitation and FA inhibition was substantially denser and probably had a lower detachment rate.
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multi species nitrifying biofilm model msnbm including free ammonia and free nitrous acid inhibition and Oxygen Limitation
Biotechnology and Bioengineering, 2010Co-Authors: Seongjun Park, Wookeun Bae, Bruce E RittmannAbstract:A multi-species nitrifying biofilm model (MSNBM) is developed to describe nitrite accumulation by simultaneous free ammonia (FA) and free nitrous acid (FNA) inhibition, direct pH inhibition, and Oxygen Limitation in a biofilm. The MSNBM addresses the spatial gradient of pH with biofilm depth and how it induces changes of FA and FNA speciation and inhibition. Simulations using the MSNBM in a completely mixed biofilm reactor show that influent total ammonia nitrogen (TAN) concentration, bulk dissolved Oxygen (DO) concentration, and buffer concentration exert significant control on the suppression of nitrite-oxidizing bacteria (NOB) and shortcut biological nitrogen removal (SBNR), but the pH in the bulk liquid has a weaker influence. Ammonium oxidation increases the nitrite concentration and decreases the pH, which together can increase FNA inhibition of NOB in the biofilm. Thus, a low buffer concentration can accentuate SBNR. DO and influent TAN concentrations are efficient means to enhance DO Limitation, which affects NOB more than ammonia-oxidizing bacteria (AOB) inside the biofilm. With high influent TAN concentration, FA inhibition is dominant at an early phase, but finally DO Limitation becomes more important as TAN degradation and biofilm growth proceed. MSNBM results indicate that Oxygen depletion and FNA inhibition throughout the biofilm continuously suppress the growth of NOB, which helps achieve SBNR with a lower TAN concentration than in systems without concentration gradients.
