scholarly journals Biofilm carrier migration model describes reactor performance

2017 ◽  
Vol 75 (12) ◽  
pp. 2818-2828 ◽  
Author(s):  
Joshua P. Boltz ◽  
Bruce R. Johnson ◽  
Imre Takács ◽  
Glen T. Daigger ◽  
Eberhard Morgenroth ◽  
...  
Keyword(s):  
Plug Flow ◽  
Biofilm Reactor ◽  
Bulk Liquid ◽  
Reactor Performance ◽  
Reactor Model ◽  
Operational Conditions ◽  
Limit Model ◽  
Biofilm Model ◽  
Reactor Models ◽  
The Impact

The accuracy of a biofilm reactor model depends on the extent to which physical system conditions (particularly bulk-liquid hydrodynamics and their influence on biofilm dynamics) deviate from the ideal conditions upon which the model is based. It follows that an improved capacity to model a biofilm reactor does not necessarily rely on an improved biofilm model, but does rely on an improved mathematical description of the biofilm reactor and its components. Existing biofilm reactor models typically include a one-dimensional biofilm model, a process (biokinetic and stoichiometric) model, and a continuous flow stirred tank reactor (CFSTR) mass balance that [when organizing CFSTRs in series] creates a pseudo two-dimensional (2-D) model of bulk-liquid hydrodynamics approaching plug flow. In such a biofilm reactor model, the user-defined biofilm area is specified for each CFSTR; thereby, Xcarrier does not exit the boundaries of the CFSTR to which they are assigned or exchange boundaries with other CFSTRs in the series. The error introduced by this pseudo 2-D biofilm reactor modeling approach may adversely affect model results and limit model-user capacity to accurately calibrate a model. This paper presents a new sub-model that describes the migration of Xcarrier and associated biofilms, and evaluates the impact that Xcarrier migration and axial dispersion has on simulated system performance. Relevance of the new biofilm reactor model to engineering situations is discussed by applying it to known biofilm reactor types and operational conditions.

Modeling phototrophic biofilms in a plug-flow reactor

2014 ◽  
Vol 70 (7) ◽  
pp. 1261-1270 ◽  
Author(s):  
J. D. Muñoz Sierra ◽  
C. Picioreanu ◽  
M. C. M. van Loosdrecht
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Plug Flow ◽  
Microbial Interactions ◽  
Bulk Liquid ◽  
Organic Loading Rate ◽  
Phototrophic Biofilms ◽  
Biofilm Model ◽  
The Impact

The use of phototrophic biofilms in wastewater treatment has been recognized as a potential option for development of new reactor configurations. For better understanding of these systems, a numerical model was developed including relevant microbial processes. As a novelty, this model was implemented in COMSOL Multiphysics, a modern computational environment for complex dynamic models. A two-dimensional biofilm model was used to study the spatial distribution of microbial species within the biofilm and along the length of the reactor. The biofilm model was coupled with a one-dimensional plug-flow bulk liquid model. The impact of different operational conditions on the chemical oxygen demand (COD) and ammonia conversions was assessed. The model was tuned by varying two parameters: the half-saturation coefficient for light use by phototrophs and the oxygen mass transfer coefficient. The mass transfer coefficient was found to be determining for the substrate conversion rate. Simulations indicate that heterotrophs would overgrow nitrifiers and phototrophs within the biofilm until a low biodegradable COD value in the wastewater is reached (organic loading rate <2.32 gCOD/(m2 d)). This limits the proposed positive effect of treating wastewater with a combination of algae and heterotrophs/autotrophs. Mechanistic models like this one are made for understanding the microbial interactions and their influence on the reactor performance.

Optimization modelling of anaerobic biofilm reactors

1994 ◽  
Vol 30 (12) ◽  
pp. 347-355 ◽  
Author(s):  
Makram T. Suidan ◽  
Joseph R. V. Flora ◽  
Pratim Biswas ◽  
Gregory D. Sayles
Keyword(s):  
Ionic Species ◽  
Gas Production ◽  
Biofilm Reactor ◽  
Operating Conditions ◽  
Reactor Performance ◽  
Monod Kinetics ◽  
Ph Changes ◽  
Biofilm Model ◽  
Steady State Model ◽  
Completely Stirred Tank Reactor

A rigorous steady state model of acetate-utilizing methanogenic biofilms is developed accounting for the mass transfer of neutral and ionic species, pH changes within the biofilm, pH-dependent Monod kinetics, chemical equilibrium, electroneutrality, gas production within the biofilm, and the presence of a concentration boundary layer (CBL). In contrast to traditional biofilm models where the pH is assumed to be constant within the biofilm, an increase in pH in acetate-utilizing methanogenic biofilms is predicted. Furthermore, significant differences can exist between the flux predictions using the traditional models and when pH changes within the biofilm are taken into account. The optimum pH for acetate-utilizing biofilms is less than the optimum defined for suspended-growth systems. The biofilm model is coupled to a model of a completely-stirred tank reactor (CSTR), and strategies for the optimization of biofilm reactor performance are examined. For a fixed set of operating conditions, an optimum influent pH can be defined that corresponds to the maximum removal efficiency and flux of acetate into the biofilm.

Systematic evaluation of biofilm models for engineering practice: components and critical assumptions

2011 ◽  
Vol 64 (4) ◽  
pp. 930-944 ◽  
Author(s):  
J. P. Boltz ◽  
E. Morgenroth ◽  
D. Brockmann ◽  
C. Bott ◽  
W. J. Gellner ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Model Calibration ◽  
Biofilm Reactor ◽  
Systematic Evaluation ◽  
Engineering Practice ◽  
Model Parameters ◽  
Concentration Gradients ◽  
Reactor Model ◽  
Biofilm Model ◽  
Calibration Protocol

Biofilm models are valuable tools for the design and evaluation of biofilm-based processes despite several uncertainties including the dynamics and rate of biofilm detachment, concentration gradients external to the biofilm surface, and undefined biofilm reactor model calibration protocol. The present investigation serves to (1) systematically evaluate critical biofilm model assumptions and components and (2) conduct a sensitivity analysis with the aim of identifying parameter subsets for biofilm reactor model calibration. AQUASIM was used to describe submerged-completely mixed combined carbon oxidation and nitrification IFAS and MBBR systems, and tertiary nitrification and denitrification MBBRs. The influence of uncertainties in model parameters on relevant model outputs was determined for simulated scenarios by means of a local sensitivity analysis. To obtain reasonable simulation results for partially penetrated biofilms that accumulated a substantial thickness in the modelled biofilm reactor (e.g. 1,000 μm), an appropriate biofilm discretization was applied to properly model soluble substrate concentration gradients and, consistent with the assumed mechanism for describing biofilm biomass distribution, biofilm biomass spatial variability. The MTBL thickness had a significant impact on model results for each of the modelled reactor configurations. Further research is needed to develop a mathematical description (empirical or otherwise) of the MTBL thickness that is relevant to modern biofilm reactors. No simple recommendations for a generally applicable calibration protocol are provided, but sensitivity analysis has been proven to be a powerful tool for the identification of highly sensitive parameter subsets for biofilm (reactor) model calibration.

scholarly journals Impact of Daptomycin Dose Exposure Alone or in Combination with β-Lactams or Rifampin against Vancomycin-Resistant Enterococci in an In Vitro Biofilm Model

2020 ◽  
Vol 64 (5) ◽  
Author(s):  
Seyedehameneh Jahanbakhsh ◽  
Nivedita B. Singh ◽  
Juwon Yim ◽  
Razieh Kebriaei ◽  
Jordan R. Smith ◽  
...  
Keyword(s):  
Bactericidal Activity ◽  
Enterococcus Faecium ◽  
Biofilm Reactor ◽  
Content Type ◽  
Biofilm Model ◽  
Vancomycin Resistant Enterococci ◽  
Dosing Regimens ◽  
Vancomycin Resistant ◽  
Reactor Models

ABSTRACT Enterococcus faecium strains are commonly resistant to vancomycin and β-lactams. In addition, E. faecium often causes biofilm-associated infections and these infections are difficult to treat. In this context, we investigated the activity of dosing regimens using daptomycin (DAP) (8, 10, 12, and 14 mg/kg of body weight/day) alone and in combination with ceftaroline (CPT), ampicillin (AMP), ertapenem (ERT), and rifampin (RIF) against 2 clinical strains of biofilm-producing vancomycin-resistant Enterococcus faecium (VREfm), namely, strains S447 and HOU503, in an in vitro biofilm model. HOU503 harbors common LiaS and LiaR substitutions, whereas S447 lacks mutations associated with the LiaFSR pathway. MIC results demonstrated that both strains were susceptible to DAP and resistant to CPT, AMP, ERT, and RIF. The 168-h pharmacokinetic/pharmacodynamic (PK/PD) CDC biofilm reactor models (simulating human antibiotic exposures) were used with titanium and polyurethane coupons to evaluate the efficacy of antibiotic combinations. DAP 12 and 14 achieved bactericidal activity against S447 but lacked such effect against HOU503. Addition of ERT and RIF enhanced DAP activity, allowing DAP 8 and 10 plus ERT or RIF to produce bactericidal activity against both strains at 168 h. While DAP 8 and 10 plus CPT improved killing, they did not reach bactericidal reduction against S447. Combination of AMP, CPT, ERT, or RIF resulted in enhanced and bactericidal activity for DAP against HOU503 at 168 h. Our data provide further support for the use of combinations of DAP with AMP, ERT, CPT, and RIF in infections caused by biofilm producing VREfm. Further research involving DAP combinations against biofilm-producing enterococci is warranted.

scholarly journals Towards advanced aeration modelling: from blower to bubbles to bulk

2016 ◽  
Vol 75 (3) ◽  
pp. 507-517 ◽  
Author(s):  
Andreia Amaral ◽  
Oliver Schraa ◽  
Leiv Rieger ◽  
Sylvie Gillot ◽  
Yannick Fayolle ◽  
...  
Keyword(s):  
Oxygen Transfer ◽  
Bubble Formation ◽  
Model Development ◽  
Plug Flow ◽  
Operating Conditions ◽  
Physical Models ◽  
Bulk Liquid ◽  
Aeration System ◽  
Modelling Studies ◽  
The Impact

Aeration is an essential component of aerobic biological wastewater treatment and is the largest energy consumer at most water resource recovery facilities. Most modelling studies neglect the inherent complexity of the aeration systems used. Typically, the blowers, air piping, and diffusers are not modelled in detail, completely mixed reactors in a series are used to represent plug-flow reactors, and empirical correlations are used to describe the impact of operating conditions on bubble formation and transport, and oxygen transfer from the bubbles to the bulk liquid. However, the mechanisms involved are very complex in nature and require significant research efforts. This contribution highlights why and where there is a need for more detail in the different aspects of the aeration system and compiles recent efforts to develop physical models of the entire aeration system (blower, valves, air piping and diffusers), as well as adding rigour to the oxygen transfer efficiency modelling (impact of viscosity, bubble size distribution, shear and hydrodynamics). As a result of these model extensions, more realistic predictions of dissolved oxygen profiles and energy consumption have been achieved. Finally, the current needs for further model development are highlighted.

The Performance of a Heat Exchanger Type Anaerobic Biofilm Reactor

1991 ◽  
Vol 24 (5) ◽  
pp. 149-161 ◽  
Author(s):  
C. R. Escalera ◽  
S. Uchida
Keyword(s):  
Heat Exchanger ◽  
Biofilm Reactor ◽  
Bulk Liquid ◽  
Inlet Temperature ◽  
Reactor Model ◽  
Consecutive Reaction ◽  
Diffusion Rates ◽  
Effects Of Temperature ◽  
And Diffusion ◽  
Primary Substrate

The performance of a heat exchanger-type anaerobic biofilm reactor(HEABR) was theoretically and experimentally studied. The treatment of a relatively low-strength artificial wastewater was experimentally feasible for a range of wall temperatures varying from 25° C to 37° C, inlet temperatures varying from 5° C to 15° C and loading rates varying from 0.2g-C/l.day to 0.8 g-C/l.day. Removal efficiencies in the range of 70–98% were obtained. It was found that the performance of the reactor is strongly dependent on the wall temperatures and the hydraulic retention times and that the inlet temperature effect is smaller. A reactor model was developed which considers that a consecutive reaction occurs both in the biofilm and the bulk liquid where the bacteria exist. The effects of temperature on the reaction and diffusion rates of the primary substrate and the intermediate product are also considered. A good fit between the experimental and calculated results showed the validity of the model.

Modelling ammonium-oxidizing population shifts in a biofilm reactor

2013 ◽  
Vol 69 (1) ◽  
pp. 208-216 ◽  
Author(s):  
T. P. W. Vannecke ◽  
N. Bernet ◽  
J.-P. Steyer ◽  
E. I. P. Volcke
Keyword(s):  
Biofilm Reactor ◽  
Bulk Liquid ◽  
Ecological Niches ◽  
Endogenous Respiration ◽  
Ammonia Oxidizing Bacteria ◽  
Mass Transfer Limitation ◽  
One Dimensional ◽  
Biofilm Model ◽  
Nitrite Oxidizing Bacteria ◽  
Different Populations

The dynamic reactor behaviour of a nitrifying inverse turbulent bed reactor, operated at varying loading rate, was described with a one-dimensional two-step nitrification biofilm model. In contrast with conventional biofilm models, this model includes the competition between two genetically different populations of ammonia-oxidizing bacteria (AOB), besides nitrite-oxidizing bacteria (NOB). Previously gathered experimental evidence showed that different loading rates in the reactor resulted in a change in the composition of the AOB community, besides a different nitrifying performance. The dissolved oxygen concentration in the bulk liquid was put forward as the key variable governing the experimentally observed shift from Nitrosomonas europaea (AOB1) to Nitrosomonas sp. (AOB2), which was confirmed by the developed one-dimensional biofilm model. Both steady state and dynamic analysis showed that the influence of microbial growth and endogenous respiration parameters as well as external mass transfer limitation have a clear effect on the competition dynamics. Overall, it was shown that the biomass distribution profiles of the coexisting AOB reflected the ecological niches created by substrate gradients.

Considering microbial and aggregate heterogeneity in biofilm reactor models: how far do we need to go?

2015 ◽  
Vol 72 (10) ◽  
pp. 1692-1699 ◽  
Author(s):  
Thomas P. W. Vannecke ◽  
George Wells ◽  
Nathalie Hubaux ◽  
Eberhard Morgenroth ◽  
Eveline I. P. Volcke
Keyword(s):  
Microbial Diversity ◽  
Granular Sludge ◽  
Biofilm Reactor ◽  
Behavior Prediction ◽  
Reactor Performance ◽  
Critical Question ◽  
Multispecies Model ◽  
Conventional Models ◽  
Reactor Models ◽  
Model Features

A model describing a given system should be as simple as possible – but not simpler. The appropriate level of complexity depends both on the type of system and on the intended use of the model. This paper addresses the critical question of which purposes justify increased complexity of biofilm (reactor) models. Additional model features compared to conventional models considered are: (1) the inclusion of microbial diversity, distinguishing between different species performing the same function; and (2) the distinction between flocs and granules in putatively granular sludge reactors. With a multispecies model considering interspecies diversity, it was demonstrated that a given macroscopic reactor performance does not necessarily reflect steady state conditions on the microscale. In a second case study, it was shown that the addition of a small level of flocs can have a significant impact on macroscale process performance and on microbial population and activity distributions in granular sludge reactors. It was concluded that increased complexity in biofilm models, concerning microbial diversity or mesoscale aggregate architecture, is likely more useful when the focus is on understanding fundamental microscale outputs, but under specific conditions, these additional model features can be critically informative for bulk reactor behavior prediction and general understanding.

Chemical stress induced by copper: examination of a biofilm system

2006 ◽  
Vol 54 (9) ◽  
pp. 191-199 ◽  
Author(s):  
X. Zhang ◽  
K. Brussee ◽  
Caroline T. Coutinho ◽  
J.N. Rooney-Varga
Keyword(s):  
Extracellular Polymeric Substances ◽  
Wastewater Treatment Plants ◽  
Intergenic Spacer ◽  
Biofilm Reactor ◽  
Copper Removal ◽  
Reactor Performance ◽  
Copper Contamination ◽  
Substrate Removal ◽  
Contamination Levels ◽  
The Impact

Biofilm systems have been widely used in wastewater treatment plants. However, little information is available on the impact of toxic chemicals on the performance of fixed film systems. This study was aimed at evaluating the impact of copper on a biofilm system by examining a variety of parameters, including reactor pH, DO, substrate concentrations, secretion of extracellular polymeric substances (EPS), and copper removal and accumulation. The microbial communities in the biofilms were also examined using automated ribosomal intergenic spacer analysis (ARISA). Four rotating drum biofilm reactors were used to produce biofilms. One reactor was used to produce biofilms under copper free conditions; while the others were used to produce biofilms grown under three different copper contamination levels, namely 100 ppb, 200 ppb, and 500 ppb, for a prolonged period. The following results were obtained: (1) biofilm reactor performance was not significantly impacted as demonstrated by the pH, DO, substrate removal, and total solids in the effluent; (2) however, copper contamination inhibited EPS production in the biofilms; (3) copper removal efficiencies of 25–31% were obtained for the three copper contamination levels studied; (4) fixed films functionalized as a reservoir to accumulate more copper over time; and (5) copper contamination selected for specific species that were able to tolerate this stress and that may contribute to its remediation.

scholarly journals Aspects of Strength Testing of Tank Containers in Compliance with the Requirements of the UN Navigation Rules and Regulations

2021 ◽  
Vol 9 (3) ◽  
pp. 349
Author(s):  
Andrii Sulym ◽  
Pavlo Khozia ◽  
Eduard Tretiak ◽  
Václav Píštěk ◽  
Oleksij Fomin ◽  
...  
Keyword(s):  
Natural Frequencies ◽  
Response Spectrum ◽  
Experimental Curve ◽  
Bulk Liquid ◽  
Frequency Range ◽  
Test Configuration ◽  
Shock Response ◽  
Shock Response Spectrum ◽  
Spectrum Curve ◽  
The Impact

This article deals with the method of computer-aided studies of the results of tank container impact tests to confirm the ability of portable tanks and multi-element gas containers to withstand the impact in the longitudinal direction on a specially equipped test rig or using a railway flat car by impacting a flat car with a striking car, in compliance with the requirements of the UN Navigation Rules and Regulations. It is shown that the main assessed characteristic of the UN requirements is the spectrum of the shock response (accelerations) for the interval natural frequencies of the shock pulse. The calculation of the points of the shock response spectrum curve based on the test results is reproduced in four stages. A test configuration of the impact testing of the railway flat car with a tank container is presented, and the impact is performed in such a way that, under a single impact, the shock spectrum curve obtained during the tests for both fittings subjected to impact repeats or exceeds the minimum shock spectrum curve for all frequencies in the range of 2 Hz to 100 Hz. Formulas for determining the relative displacements and accelerations for the interval natural frequencies of the shock wave are given. The research results are presented in graphical form, indicating that the experimental values of the shock response spectrum exceed the minimum permissible values; the equation of the experimental curve of the shock response spectrum in the frequency range 0–100 Hz is described by power-law dependence. The coefficients of the equation were determined by the statistical method of maximum likelihood with the determination factor being 0.897, which is a satisfactory value; a comparative analysis showed that the experimental curve of the impact response spectrum in the frequency range 0–100 Hz exceeds the normalized curve, which confirms compliance with regulatory requirements. A new test configuration is proposed using a tank car with a bulk liquid, the processes in which upon impact differ significantly from other freight wagons under longitudinal impact loads of the tank container. The hydraulic impact resulting from the impact on the tank container and the platform creates an overturning moment that causes the rear fittings to be unloaded.

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