A dynamic model describing styrene abatement was developed for a two-phase partitioning bioreactor operated as a biotrickling filter (TPPB-BTF). The model was built as a coupled set of two different systems of partial differential equations depending on whether an irrigation or a non-irrigation period was simulated. The maximum growth rate was previously calibrated from a conventional BTF treating styrene (Part 1). The model was extended to simulate the TPPB-BTF based on the hypothesis that the main change associated with the non-aqueous phase is the modification of the pollutant properties in the liquid phase. The three phases considered were gas, a water–silicone liquid mixture, and biofilm. The selected calibration parameters were related to the physical properties of styrene: Henry’s law constant, diffusivity, and the gas–liquid mass transfer coefficient. A sensitivity analysis revealed that Henry’s law constant was the most sensitive parameter. The model was successfully calibrated with a goodness of fit of 0.94. It satisfactorily simulated the performance of the TPPB-BTF at styrene loads ranging from 13 to 77 g C m-3 h-1 and empty bed residence times of 30–15 s with the mass transfer enhanced by a factor of 1.6. The model was validated with data obtained in a TPPB-BTF removing styrene continuously. The experimental outlet emissions associated to oscillating inlet concentrations were satisfactorily predicted by using the calibrated parameters. Model simulations demonstrated the potential improvement of the mass-transfer performance of a conventional BTF degrading styrene by adding silicone oil.
En l’actual context econòmic l’aprofitament de materials residuals que tenen un potencial econòmic hauria de ser prioritari. En aquest sentit, la creixent producció de residus elèctrics i electrònics converteix aquests materials en una potencial font de metalls molt valuosos i escassos. És per aquest motiu que és de vital importància desenvolupar noves tecnologies de valorització de metalls, que siguin econòmicament més rentables, sostenibles i respectuoses amb el medi ambient. Els últims informes oficials quantifiquen en 40 milions de tones al any les deixalles electròniques en el món. L’elevat consum de telèfons mòbils, a banda d’altres electrodomèstics com ordinadors o televisors, fa que la generació de residus electrònics s’hagi convertit en un greu problema global, sent el tipus de residu que creix a major velocitat (entre el 3-5% anual). En aquests residus es troba un elevat percentatge de metalls (40%) amb possibilitats de ser reutilitzats, com són el coure, crom, zinc, níquel, alumini o metalls precisos (or, plata i platí). Tenint en compte que el percentatge d’aquests metalls en els residus és generalment major (10-20%) que en la font natural d’on s’extreuen (0.5-3%) i que aquests es troben localitzats en jaciments molt específics del planeta, l’èxit d’aquesta proposta significa un doble avantatge, aconseguir una font alternativa i sostenible de metalls i gestionar un residu molt perillós per a la salut humana i l’ecosistema.
La solució que es proposa per aquest problema consisteix en aprofitar l’activitat metabòlica de determinats microorganismes (fonamentalment bacteris), per a regenerar els agents responsables d’extreure els metalls de la matriu on es troben immobilitzats una vegada finalitzada la vida útil de l’aparell electrònic que els conté (residu). La viabilitat d’aquest procés redueix significativament els costos energètics i l’ús de reactius agressius en comparació amb els processos convencionals que es porten a terme en centres molt específics que han de tractar grans volums de deixalles per convertir el procés de recuperació en quelcom rentable.
A three-phase dynamic mathematical model based on mass balances describing the main processes in biotrickling filtration: convection, mass transfer, diffusion, and biodegradation was calibrated and validated for the simulation of an industrial styrene- degrading biotrickling filter. The model considered the key features of the industrial operation of biotrickling filters: variable conditions of loading and intermittent irrigation. These features were included in the model switching from the mathematical description of periods with and without irrigation. Model equations were based on the mass balances describing the main processes in biotrickling filtration: convection, mass transfer, diffusion, and biodegradation. The model was calibrated with steady-state data from a laboratory biotrickling filter treating inlet loads at 13–74 g C m-3 h-1 and at empty bed residence time of 30–15 s. The model predicted the dynamic emission in the outlet of the biotrickling filter, simulating the small peaks of concentration occurring during irrigation. The validation of the model was performed using data from a pilot on- site biotrickling filter treating styrene installed in a fiber-reinforced facility. The model predicted the performance of the biotrickling filter working under high-oscillating emissions at an inlet load in a range of 5–23 g C m-3 h-1 and at an empty bed residence time of 31 s for more than 50 days, with a goodness of fit of 0.84.
BACKGROUND: The removal of problematic volatile organic compounds (VOCs) from polluted gas (toluene, iso-octane and hexane) has been investigated in amembrane bioreactor (MBR) by adapting a commercial capillarymicroporous polypropylene membrane. TheMBRperformancewasmeasuredunder several operational conditions. The influenceof theemptybedresidence time (EBRT), the liquid velocity and the inlet concentration was evaluated.
RESULTS: For toluene, itwas possible to treat higher loading rates than 1600 gm-3 h-1 with amaximum elimination capacity (EC) of 1309 g m-3 h-1, removal efficiencies (RE) of ~80%. However, iso-octane was poorly degraded as a single pollutant. Hexane presented lower EC values (400 g m-3 h-1) than toluene. The synergistic effect of hexane degradation in two different mixtures was also considered.
CONCLUSION: Results demonstrate that a commercial membrane for wastewater treatment can be adapted for biological gas treatment, becoming a potential alternative to conventional biological treatment technologies, especially for pollutants with low solubility.
Prades, L.; Arnau, R.; Chiva, S.; Dorado, A.D.; Gamisans, X. International Conference on Biotechniques for Air Pollution Control and Bioenergy p. 65-67 Data de presentació: 2017-07-20 Presentació treball a congrés
In biofiltration systems, the gas/liquid interphase acts as a major medium for the transport of dissolved solutes into and out of the biofilm. Therefore, transfer processes can be affected by the reactor flow conditions (Trejo-Aguilar et al., 2005), so an adequate characterization of this fluid flow is required in order to describe accurately the system, jointly with the biological behavior. Several mathematical models, from plug flow to computational fluid dynamic (CFD), have been used to describe hydrodynamics when modeling bioreactors performance. Comparing performance-prediction of this various models for the most common aerobic bioreactors, Liotta et al. (2014) concluded that CFD models are the most complete because they describe the hydrodynamic phenomena more in detail, considering the local processes that take place in the reactor. Hence, CFD techniques have been employed as a useful tool for understanding multiphase hydrodynamics and biochemical reactions in airlift and activated sludge reactors in wastewater treatment (Feng et al., 2007; Le Moullec et al., 2010, Liotta et al., 2014), where the bioreaction behavior is associated to the liquid phase dynamics. Nevertheless, the complicated interactions between biofilm and fluid flow phases, coupling the hydrodynamics with mass transfer between phases and bioreactions in biofilm, have not been described using this type of techniques, being a key parameter to optimize the biofiltration systems performance and improve their knowledge.
The aim of this investigation is to develop more comprehensive models for biofiltration processes by incorporating fluid flow dynamics coupled with mass transfer and biokinetics. A multiphase model was developed to describe biofilm and phases interaction in a bioreactor.
The commercial CFD software ANSYS® Academic Research, Release 16.2, was used to solve the equations of continuity and momentum. The model was defined by a single domain, and the region of the biological system was introduced as a subdomain. The implementation of biological reactions in the CFD code was performed using the methodology described by Climent et al. (2014). Related to mass transfer phenomena, empirical correlations and coefficients were defined between the components of the phases. Simulations were calculated either in transient and steady state. In both states, laminar flow regime was defined.
The 3D CFD model, combining hydrodynamics and biochemical reactions, was developed and solved to simulate local flow and the dynamic behavior of biofilm
growth and species biodegradation. In order to know the effect of mass transport phenomena (advection and diffusion), the results of CFD simulations were evaluated by characterizing hydrodynamics and the prediction of the pollutant degradation along the bioreactor. Moreover, the CFD simulation results were validated by comparing simulated results with experimental data. The simulated predictions illustrated a satisfactory agreement with experimental data, reproducing consistently pollutant degradation in the bioreactor, decreasing its concentration from the inlet to the outlet
Prades, L.; Bautista, Y.; Climent, J.; Sanz, V.; Chiva, S.; Dorado, A.D.; Gamisans, X. International Conference on Biotechniques for Air Pollution Control and Bioenergy p. 102-104 Data de presentació: 2017-07-20 Presentació treball a congrés
Biofilms are considered as microbial communities attached to a surface where they grow as fixed films and interact with the media through the phases that flows over them. Biofilms form complex structures containing mainly microorganisms, nucleic acids, proteins, extracellular polymeric substances (EPS) (Sutherland, 2001) which provide them of specific mechanic properties (Wilking et al., 2011). The shear stress caused by the fluid flow over fixed biofilms is a factor of paramount importance which influences their development (growing and detachment) and, hence, affecting the system operation. A deeper knowledge in the characterization of the effect of flow on biofilms development could allow establishing rigorous models able to predict a closer behavior to real systems.
The aim of this study was to investigate extensively the rheological properties of heterotrophic biofilms present in bioreactors by performing rheological tests and models development. Considering a viscoelastic behavior, a detailed experimental program was accomplished to test the response of biofilms under steady shear, oscillatory and transient measurements. To develop a complete characterization, suspended biomass (SB) samples were also analyzed, comparing their rheological behavior with that obtained from the biofilms, i.e. fixed biomass, under different flow conditions.
In the steady shear mode, equilibrium flow curve measurements were conducted with controlled shear stress and raising it stepwise. In the oscillatory shear mode, amplitude sweep test was performed to determine the effect of shear stress on G' and G¿, determining the linear viscoelastic regimen (LVR) with a tolerance of 10% for the strain limit value. In the transient shear mode, shear creep tests were performed by applying a constant shear stress inside the LVR (40 Pa) and measuring shear strain (¿) over time.
Biofilms (32.6 and 34.5 g VSS L-1) and suspended biomasses (from 8 to 43 g VSS L-1) were analyzed in the steady shear flow (Figure 1). Their shear-thinning behavior with a yield stress was identified, fitting the data results with Herschel-Bulkley model (Mezger, 2006). These results allowed us to model their rheological behavior as non-newtonian fluids, and to correlate the rheological parameters in function of the concentration samples. In oscillatory shear flow analysis of biofilms and SB samples (Figure 2A), the elastic behavior dominated the viscous one inside the LVR, showing their gel character, but with some inequalities in their structure and viscoelastic properties. Similar behavior was also observed under transient shear flow test (Figure 2B), where the deformation of biofilm was much greater than in the SB samples. The Burger model (Towler et al., 2003) described rightly the strain of both samples.
Guimera, X.; Mora, M.; López, L.; Dorado, A.D.; Gamisans, X.; Lafuente Sancho, Francisco Javier; Gabriel, D. International Conference on Biotechniques for Air Pollution Control and Bioenergy p. 57-59 Data de presentació: 2017-07-20 Presentació treball a congrés
An improved monitoring technique for biofilm activity assessment, named heterogeneous respirometry (HR), was applied to characterize sulfide-oxidizing biofilms. In the HR, the aerobic oxidation of sulfide can be studied directly within the colonized packing material. The HR can also be mathematically modelled considering the gas, liquid and biofilm phases. Nevertheless, the interpretation and modelling of oxygen profiles in the liquid and gas bulk phases of a HR is complex since mass transport phenomena between gas, liquid and biofilm phases must be considered. Moreover, reliable kinetic models describing trickled beds must consider the biodegradation processes and activity occurring along the biofilm thickness. Dissolved oxygen microsensors (DO-MEA) could be highly adequate to characterize sulfide oxidizing biofilms since have been successfully applied to characterize other type of biofilms (Guimerà et al., 2015).
The aim of this work was to improve the HR technique used in previous works (Bonilla-Blancas et al. 2015) by using a DO-MEA sensor during respirometric tests to obtain 8 simultaneous DO profiles in 1 mm of biofilm. This work also aimed at modelling the DO profiles obtained. The experimental system used in this work consisted of a lab-scale BTF, manufactured in PVC, with a bed diameter and height of 0.06 m and 0.23 m, respectively. The reactor run as a differential reactor with the liquid and gas phases continuously recirculated in counter-current mode through the packed bed after a substrate pulse addition. Further details about the experimental setup can be found elsewhere (Bonilla-Blancas et al. 2015). HR was provided with an oxygen gas analyzer, a galvanic DO sensor placed on liquid phase recirculation, and a sampling port for microsensors monitoring. DO monitoring within the biofilm was performed using a DO microsensor (DO-MEA sensor) based on microfabrication technology as described elsewhere. This microsensor, specially designed for biofilm profiling, consisted of an array of eleven gold-disk working electrodes, with a spacing of 125 µm mounted on a minimally invasive microfabricated needle. Many experiments were performed to characterize G-L mass transfer phenomena (abiotic tests to estimate the overall volumetric mass transfer coefficient) and the H2S-oxidizing activity (biotic assays with colonized Pall rings from a desulfurizing biotrickling filter to estimate biomass density and the endogenous and maximum oxidation rates within the biofilm). To characterize the activity, HR was closed and many pulses of H2S were injected in the respirometer (200µL, 1mL, 5mL and 10mL), which corresponded to initial gas phase concentrations ranging from 135 ppmv to 6720 ppmv (Figure 1). Oxygen evolution through the HR was
used to validate the biokinetic model included in the mathematical model developed to describe HR operation and to obtain physical-chemical parameters.
As can be observed in Figure 1A and 1B, the monitoring of dissolved oxygen is much more sensitive than the monitoring of oxygen concentration in the gas phase. Moreover, respirometric profiles obtained from the biofilm monitoring allowed confirming that using this methodology oxygen limitations in the inner layers of biofilm can be clearly assessed and characterized (Figure 1B and 1D). The mathematical model developed in this work to describe the respirometric profiles (data not shown) took into account the physical, chemical and biological processes occurring in this process.
San Valero, P.; Quijano, G.; Dorado, A.D.; Alvarez, F.; Martínez-Soria, V.; Gabaldón, C. International Conference on Biotechniques for Air Pollution Control and Bioenergy p. 3-5 Data de presentació: 2017-07-20 Presentació treball a congrés
Biotrickling filters (BTFs) are a well-accepted end-of-pipe solution for the treatment of air emissions laden with volatile organic compounds (VOCs), being their performance markedly dependent on the physical properties of the target pollutant to remove. In the case of low soluble compounds like styrene, the rate limiting step of the process usually deals with the mass transfer between the gas and the liquid phase. The addition of silicone oil as a non-aqueous phase has been demonstrated as a promising strategy, enhancing the performance for styrene removal in BTFs (Rene et al., 2011). The development of a systematic protocol would be needed to introduce this process to the industry. In this regard, mathematical models using a phenomenological approach has been demonstrated useful to improve the understanding of the governing processes (Dorado et al., 2015). The aim of this work is the evaluation of a two-phase partitioning reactor (TPPB) operated as a BTF treating styrene under typical industrial operation conditions in order to expand the niche market of the technology. This work comprises the experimental assessment of styrene removal and the dynamic simulation of the TPPB-BTF by extending the use of the model for BTFs developed by San-Valero et al. (2015).
The TPPB-BTF was studied at low empty bed residence times (EBRTs) varying from 30 to 15 s, which is the experimental boundary found for BTFs treating styrene. The resilience of the TPPB-BTF was also evaluated by the application of styrene shock loadings under transient conditions. The results obtained showed that the TPPB-BTF was able to successfully treat styrene air emissions at EBRTs as shorter as 15 s, which is the shortest so far tested at literature. The TPPB-BTF achieved stable removal efficiencies of up to 84% at inlet loadings of up to 22 g C m-3 h-1 (inlet concentration = 92 mg C m-3). It is noteworthy that under the same conditions the control BTF without silicone oil achieved a RE of 42 % (San-Valero et al., 2017). The robustness of the TPPB-BTF was also confirmed by keeping removal efficiencies at 89% after styrene shock loadings of up to 645 mg C m-3.
A dynamic model describing the styrene abatement and oxygen consumption was developed for a BTF with a non-aqueous phase and discontinuous irrigation based on a previous authors’ model (San-Valero et al., 2015). The model was built as a coupled set of two different systems of partial differential equations depending on whether an irrigation or a non-irrigation period was simulated. Mass transfer coefficient and maximum growth rate were previously calibrated from a BTF treating styrene operating in conventional mode. From this point on, the model was extended to simulate the TPPB-BTF based on the hypothesis that the main change associated to the non-aqueous phase lies on the modification of the properties of the pollutant in the liquid phase. Thus, the
three phases considered were gas, mixed-water/silicone liquid and biofilm. The selected calibration parameters were related to physical properties of styrene: the Henry’s law constant, the diffusivity and the gas-liquid mass transfer coefficient. A sensitivity analysis was performed revealing that the Henry’s constant was the most sensitive parameter. The model was successfully calibrated with a goodness of fit of 94%, being able to simulate satisfactorily the performance at several ILs from 13 to 77 g C m-3 h-1 and EBRTs from 30 to 15 s. The validation of the model was carried out from data of the continuous monitoring of the TPPB-BTF at loading changes that simulate industrial operation. Model was capable of predicting the dynamic behavior experimentally observed with high agreement. The enhancement on the performance of the TPPB-BTF versus BTF at EBRT of 15 s is shown in Figure 1, jointly with model simulation at the same conditions tested.
Guimera, X.; Moya, A.; Rodríguez, D.; Gabriel, D.; Villa, R.; Dorado, A.D.; Gabriel, G.; Gamisans, X. International Conference on Biotechniques for Air Pollution Control and Bioenergy p. 108-110 Data de presentació: 2017-07-20 Presentació treball a congrés
Technical limitations existing for the study and monitoring of biofilms, have been virtually solved from the development of a wide range of microsensors (Santegoeds et al., 1998). These devices allow monitoring chemical microgradients and bacterial activity within biofilms with a high spatial resolution. However, available microsensors are extremely fragile and expensive instruments, and require additional and sophisticated equipment to control their positioning. These limitations have prevented a widespread use for biofiltration systems monitoring. To reduce these limitations, microelectromechanical systems (MEMS) technology have been used in microsensors design and fabrication. This technology provides a more versatile approach, allowing specific design for particular applications (Liu et al., 2009). MEMS technology enables the fabrication of more robust devices, ensures cost-effective, massive production of identical microsensors.
In this work a novel microsensor, based on MEMS technology, specially designed for the simultaneous monitoring of dissolved oxygen (DO) and pH is presented. This microsensor was specially designed for biofilms profiling, and enables simultaneous DO and pH monitoring along time, at different biofilm locations. The aim of this work is to show the capabilities of these microsensors for biofiltration process monitoring, obtaining continuous information of both species microgradients within biofilms.
The microsensor was fabricated through standard photolithographic techniques. The substrate was a 125 µm thick Kapton layer, in which 7 Au electrodes and 7 Pt electrodes were linearly arranged. Pt electrodes were coated with an Iridium Oxide (IrOx) layer by an electrochemical procedure for pH monitoring. The microsensor also include two extra electrodes to complete an electrochemical measurements system. A biggest one was designed to work as Counter Electrode (CE), while a smallest one was designed to work as pseudo-Reference Electrode (pRE). The fabrication procedure was completed by two Ink-Jet printing steps. These steps allowed the integration of a stable Ag/AgCl pRE within the needle, printing silver nanoparticle ink onto the selected electrode which was subsequently chlorinated. Finally, the fabrication was completed printing a Poly (2-hydroxyethyl methacrylate) (pHEMA) membrane coating the electrodes in order to avoid their fouling.
The microsensor performance for both species detection was exhaustively characterized.
Experimental sensitivities were quantified at 2.06±0.08 nA·mg-1·L for DO detection, and
at 61.2±0.7 mV·pH-1 for pH detection. Besides, pRE and protective membrane ensures a stable response along time, allowing long term measurements and therefore opening up the possibility of continuous biofilms monitoring within biofiltration systems.
The suitability of the microsensor for DO and pH continuous monitoring was evaluated in an autotrophic sulphur-oxidizing biofilm grown on a lab-scale, flat-plate biofilm reactor. The microsensor was used to record DO and pH evolution at different depths within biofilm in front of different operational scenarios, shown in Figure 1.
Results obtained during biofilm monitoring using the novel microsensor allowed investigating the dynamics of both species during the reactor operation. On one hand, DO evolution presented in Figure 1a-c showed the presence of anaerobic zones in the inner biofilm depths, and on the other hand, the flat pH profiles demonstrated a high protons diffusion rate.
Microsensors have become a powerful tool in the development of biofiltration techniques for gaseous pollutants abatement, from the information obtained in situ within biofilms. Concentration profiles recorded using microsensors allow the determination of mass transport and biokinetics parameters. Different microsensors, based on microelectromechanical systems (MEMS) have been developed recently, to overcome most of the conventional Clark-type microsensors limitations. Taking into account that dissolved oxygen and pH are critical parameter in biofilm reactors, a new microsensor has been developed by including a second array of microelectrodes added in parallel to a previously developed dissolved oxygen (DO) sensor. Microelectrodes used for pH sensing are platinum based electrodes modified using electrodeposited iridium oxide technology. Results from this work show the complete characterization and validation of the multi electrode as a powerful tool for simultaneous pH and DO profiling of biofilms in different types of fixed bed bioreactors.
The influence of fluid flow dynamics in mass transfer and biokinetics was considered to develop a rigorous model for biofiltration processes in air pollution control. In particular, a 3D model has been developed employing CFD techniques to analyze the impact of hydrodynamics over mass transfer and to predict biofilm activity and space-time evolution of physical and biological phenomena involved. The rheology considered for the fixed biofilm has been experimentally characterized. The dynamic multiphase model describes biofilm and liquid phase interaction. Moreover, model predictions were corroborated with direct measurements in the interphase and within the biofilm by means of novel microsensors with high spatial resolution. Model predictions improved in comparison to conventional diffusional-reaction model and well-established modeling tools. Therefore, the developed and validated model becomes a valuable tool to characterize in detail main processes taking place in the interface and within the fixed-bed biofilm, and finally to optimize bioreactors operation.
Guimera, X.; Mora, M.; López, L.; Dorado, A.D.; Gamisans, X.; Lafuente Sancho, Francisco Javier; Gabriel, D. International Conference on Biofilm Reactors p. 1-5 Data de presentació: 2017-05-10 Presentació treball a congrés
In this study, respirometry of heterogeneous media is advised as a valuable technique for characterizing mass transport and biological activity of H2S-oxidizing biofilms growing attached to a trickling bed. Controlled flows of liquid and H2S-containing air were recirculated through a closed heterogeneous respirometer while oxygen concentration through gas, liquid and biofilm phase was simultaneously recorded. Respirometer monitoring results were used to calibrate a model developed to describe the HR operation. Results highlighted that using DO concentration within biofilm in model calibration improve microbial activity characterization, obtaining a more accurate parameters estimation.
Arellano-Garcia, L.; Dorado, A.D.; Fortuny, M.; Gabriel, D.; Gamisans, X.; González, A.; Hernández, S.; Lafuente Sancho, Francisco Javier; Monroy, O.; Mora, M.; Revah, S.; Sierra, H. Data de publicació: 2017-04 Llibre
El presente libro aborda la obtención y el aprovechamiento del biogás como fuente energética, que se produce por digestión anaeróbica de material orgánico proveniente de distintas fuentes (vertederos, plantas de tratamiento de residuos urbanos, residuos agroindustriales y cultivos energéticos, entre otras). La Unión Europea, China y,
en menor extensión, Norteamérica son actualmente los principales productores de biogás. Recientemente, Italia, México, Nepal y Eslovenia han incrementado de forma significativa su participación en la producción global de biogás al pasar el umbral del 2 %. Se describen y discuten las técnicas disponibles para el tratamiento del biogás basadas en: contaminantes presentes, como el sulfuro de hidrógeno (H2S), el dióxido de carbono (CO2) y otros, y su variación en concentración según la fuente de origen y los daños que estos provocan; las tecnologías disponibles de purificación y enriquecimiento a biometano; una discusión sobre el uso óptimo de las tecnologías
de tratamiento según el tamaño de la planta productora de biogás, las formas de utilización, ya sea mediante uso directo o inyección en red, y el almacenamiento según el tipo de consumo energético.
Prades, L.; Dorado, A.D.; Climent, J.; Guimera, X.; Chiva, S.; Gamisans, X. Chemical engineering journal Vol. 313, p. 680-692 DOI: 10.1016/j.cej.2016.12.107 Data de publicació: 2016-12-26 Article en revista
Rigorous modeling of transport phenomena is essential to reproduce accurately biofiltration systems performance.
In this sense, the aim of this study was to investigate the effect of integrating fluid flow dynamics in the development of these bioreactor models, mimicking their hydrodynamics and behavior in a
fixed biofilm reactor. 2D bioreactor models were developed using three different well-established tools for modeling bioreactors (AQUASIM, MATLAB, and Computational Fluid Dynamics – CFD), considering from ideal flow patterns to more complex fluid dynamics. A detailed comparison was performed among the results, taking into account the simulation of dissolved oxygen profiles in the liquid phase, inside the biofilm and in the boundary layer along a bioreactor. These models were validated by comparing the simulations with direct measurements obtained by means of dissolved oxygen microsensors of high spatial resolution. In all cases, deviations were below 6%, nevertheless CFD predictions obtained the lowest deviations below 3.5%. Thus, these results underline that CFD techniques are appropriate to model more accurately the performance of fixed-bed biofilm reactors, allowing the study in detail of all the hydrodynamics variables involved in the process. In addition, a 3D CFD model, combining hydrodynamics and biological reactions, was developed and solved to simulate local transient flow and dynamic behaviors of oxygen consumption in the bioreactor. The results of CFD simulations were evaluated in order to know the effect of mass transport phenomena (advection and diffusion) by characterizing hydrodynamics and, finally, to predict the oxygen degradation along the bioreactor.
Guimera, X.; Dorado, A.D.; Gabriel Buguña, Gemma; Gabriel, D.; Gamisans, X. Jornada Nacional de Bioprocesos para el tratamiento de aire p. 12-13 Data de presentació: 2016-11-17 Presentació treball a congrés
Modelling studies highlighted that biofilms models reliability increased using parameters computed from measurements performed within biofilms . For this reason, microsensors measurements have become an essential tool in biofiltration systems modelling , allowing to advance in biofiltration technology optimization.
Micro-electromechanical systems (MEMS) technology was utilized to design and produce microsensors for simultaneous dissolved oxygen (DO) and pH detection, with the purpose of improve conventional microsensors available commercially for biofilms monitoring. The validation of these devices showed significant improvement when compared to conventional microsensors. The multi-electrode design of this device, allowed to obtain simultaneous information of DO concentration and pH at different depths inside a biofilm, with an excellent sensitivity and a high spatial resolution (<50 µm).
Biofilms monitoring was used to quantify mass transport and biodegradation rates of pollutants and substrates within biofilms. Results were used in the development of empirical correlations for the estimation of mass transport rates within biofilms, considering the influence of hydrodynamic conditions and the biofilm structure. In addition, DO, hydrogen sulphide and pH profiles recorded inside biofilms were used in the development of specific biokinetic models, which describe accurately the activity of microorganisms growing inside heterotrophic and sulphide-oxidizing biofilms. On the other hand, MEMS microsensors were also tested to monitor biotrickling filters operation, obtaining instantaneous information of DO concentration at different depths inside biofilms.
The studies conducted using these devices contributes significantly to identify the mechanisms controlling biofilms performance, and underline that these microsensors are an optimal tool for biofilms characterization and monitoring.
Prades, L.; Dorado, A.D.; Guimera, X.; Climent, J.; Chiva, S.; Gamisans, X. Jornada Nacional de Bioprocesos para el tratamiento de aire p. 14-15 Data de presentació: 2016-11-17 Presentació treball a congrés
In biofiltration systems, the gas/liquid interphase acts as a major medium for the transport of dissolved solutes into and out of the biofilm. Therefore, transfer processes can be affected by the reactor flow conditions, so an adequate characterization of this fluid flow is required in order to describe accurately the system, jointly with the biological behavior. Computational fluid dynamics (CFD) techniques have been employed as a useful tool for understanding multiphase hydrodynamics and biochemical reactions in wastewater treatment field (Liotta et al. 2014), where the bioreaction behavior is associated to the liquid phase dynamics. Nevertheless, the complicated interactions between biofilm and fluid flow phases, coupling hydrodynamics with mass transfer and bioreactions, has not been described using this type of techniques, being the key to optimize biofilters performance.
The aim of this investigation is to develop more rigorous models for biofiltration processes incorporating fluid flow dynamics. Biological kinetics expressions were implemented into CFD code and, in order to confer identity models, the CFD simulation results were compared qualitative and critically with results obtained from a conventional diffusion-reaction model and also with results of a well-established modeling tool, such as AQUASIM. Moreover, a multiphase model was developed to describe biofilm and liquid phase interaction, defining mass transfer models between the phases. The resulting CFD models, combining hydrodynamics and biochemical reactions, were developed and solved to simulate local transient flow and the dynamic behavior of species biodegradation. CFD simulation results were validated by both experimental hydrodynamic characterization and by comparing simulated results with experimental concentration micro profiles. Simulated predictions illustrated a satisfactory agreement with experimental data inside and outside the biofilm, showing that the developed CFD models are a valuable tool to study the influence of hydrodynamics over mass transport and biodegradation anywhere in the bioreactor.
Hernández, J.; Dorado, A.D.; Lafuente Sancho, Francisco Javier; Gamisans, X.; Jesús, Ó.; Gabriel, D. Environmental progress & sustainable energy Vol. 36, num. 1, p. 171-179 DOI: 10.1002/ep.12491 Data de publicació: 2016-10-07 Article en revista
Biotrickling filters for waste gas treatment are often packed with expensive, inert packing materials. In this work, poplar and pine wood chips were evaluated as low-cost packing materials in two biotrickling filters for the simultaneous treatment of a mixture of organic and inorganic volatile compounds. Bioreactors were operated at gas contact times of 22–34 s. Inlet loading rates of 3.5¿±¿1.0 gN-NH3 m-3h-1 and 6.5¿±¿1.1 gS-H2S m-3h-1 were supplied, while ethylmercaptan and butyric acid were fed at loads of 3.6¿±¿1.2 and 6.0¿±¿2.1 g m-3h-1, respectively. A thorough characterization of both packing materials revealed some differences in the physical–chemical properties, mainly in their water retentivity and buffer capacity. Despite of such differences, both bioreactors performed similarly. Bioreactors were able to achieve complete removal of NH3 and butyric acid, while H2S and EM removal efficiencies over 90% and 70%, respectively, were found. N-species analyses in the leachate proved high nitrification rates in both biotrickling filters. Control of pH was essential for maintaining nitrification activity. Other oxidation processes were hardly affected by pH changes. Both woods showed potentially attractive as packing materials for biofiltration. Thus, availability and durability of woods are decisive factors to tip the balance. The work compares the performance of two biotrickling filters packed with two types of wood chips commonly used in biofilters. No previous works have directly compared the performance of two types of woods in biotrickling filters for the treatment of a range of organic and inorganic odorants because biotrickling filters are commonly packed with inert packing materials. Results indicated that the two types of woods tested behaved similarly and, more interestingly, showed equivalent treatment capacities than that of inert packing materials in the removal of a range of typical pollutants in odorant waste gases. Research is of particular interest for improving biofiltration knowledge. In addition, this research has large practical implications in the cost-benefit of full-scale biotrickling filtration systems because inorganic packing materials commonly used in biotrickling filters are much more expensive than organic packing materials.
Esta tesis se centra en el desarrollo de nuevos microsensores diseñados específicamente para la monitorización de biopelículas y en su aplicación para el estudio y caracterización de biopelículas de diferente origen (heterótrofas y autótrofas). Utilizando tecnología de sistemas micro-electromecánicos se ha diseñado, fabricado y validado un microsensor amperométrico para la detección del oxígeno disuelto (OD), que mejora las prestaciones de los microsensores disponibles. El diseño multi-electrodo de este dispositivo permite obtener información simultánea de la concentración de OD en 8 puntos diferentes a lo largo de una biopelículas, con una excelente sensibilidad para la detección del OD y una elevada resolución espacial (<50 µm). La elevada robustez que presenta este tipo de dispositivos ha sido aprovechada para monitorizar biofiltros percoladores, obteniendo información a tiempo real de la concentración de OD en el interior de las biopelículas. La monitorización de las biopelículas heterótrofas ha servido para cuantificar en su interior las velocidades de transporte de materia. Estos resultados han sido utilizados para incrementar el conocimiento sobre los mecanismos que intervienen en estos procesos y para establecer la relación entre estos mecanismos, las condiciones hidrodinámicas del sistema y la estructura de la biopelícula. La información obtenida en estos estudios ha demostrado la importancia de incluir la heterogeneidad de las biopelículas en la descripción del transporte de materia, y ha sido utilizada para desarrollar dos correlaciones para la estimación de las velocidades de transporte de materia en el interior de las biopelículas estudiadas. La monitorización de biopelículas también se ha utilizado para desarrollar modelos cinéticos específicos para sustituir los modelos desarrollados en cultivos en suspensión, utilizados tradicionalmente para describir la actividad de biopelículas. A partir de la adquisición de perfiles de OD, H2S y pH en el interior de biopelículas ha sido posible calibrar modelos cinéticos que describen con precisión la actividad de microorganismos en el interior de biopelículas heterótrofas y sulfuroxidantes. Las medidas obtenidas con microsensores demostraron ser una excelente herramienta para validar los modelos de biofiltración y predecir con mayor precisión su comportamiento a partir de la caracterización del transporte de materia y la biocinética. Los resultados obtenidos en la simulación demostraron que la utilización de medidas directas en el interior de biopelículas, como elementos centrales del proceso biotecnológico, aumenta la rigurosidad de los modelos de biofiltración. La metodología desarrollada permitió diseñar un nuevo microsensor MEMS, basado en el de OD, que incorporó en un solo dispositivo la medida de OD y pH. El diseño y la fabricación del primer prototipo se modificaron para incluir una segunda matriz de electrodos para la detección potenciométrica del pH y para incorporar mejoras. La reducción de las dimensiones del microsensor y la protección de los electrodos hizo menos invasiva su medida y aumentó la estabilidad de su respuesta. Estas mejoras sitúan el microsensor como una herramienta de gran potencial, alternativa a los sistemas de monitorización convencionales, que permite obtener información simultánea espacial y temporal de la concentración de OD y pH en el interior de biopelículas con bajo grosor.
This thesis is focused on the development of microsensors specially designed for biofilms monitoring and on the application of these devices to study and characterize different biofilms.
Using micro-electromechanical systems (MEMS) technology, an amperometric microsensor for DO monitoring, which improves the performance of the available microsensors, has been designed, constructed and validated. The multi-electrode design of these device, allows to obtain simultaneous information about dissolved oxygen (DO) concentration at 8 different depths through a biofilm, with an excellent DO sensitivity and a high spatial resolution (<50 µm). The high robustness exhibited by the microsensor has been exploited for the monitoring of biotrickling filters, obtaining instantaneous information of DO concentration inside biofilms.
Heterotrophic biofilms monitoring has served to quantify mass transport rates within biofilms. These results have been used to increase the knowledge of mechanisms involved in these processes and to establish the relationship between mass transport mechanisms, hydrodynamic conditions and biofilm structure. The information obtained in these studies highlighted how important is to include biofilms heterogeneity in mass transport description, and has been used in the development of two correlations for the estimation of mass transport rate within biofilms.
Biofilms monitoring has been also used in the development of specific kinetic models to replace those developed in suspension cultures, used conventionally to describe biofilms activity. From DO, H2S and pH recorded profiles was possible to calibrate kinetic models, which accurately described the activity of heterotrophic and sulfuroxidizing biofilms. Microsensors measurements proved to be an excellent tool to validate biofiltration models and to more accurately predict their behaviour from the characterization of mass transport and biokinetic. Results obtained during the simulations revealed that using microsensors measurements within biofilms, as central elements of bioprocess, increase the thoroughness and the ability to accurately predict the behavior of biofilms.
The developed methodology allowed to design a novel MEMS microsensor, based on DO microsensor, integrating into a single device DO and pH measurement. The design and construction of the firts prototype was modified to include a second microelectrodes array to potentiometric pH detection, and some improvements. The reduction of microsensors dimensions and the protection of microelectrodes reduced biofilm perturbations during needle insertion and increased sensor response stability. These improvements place the microsensor as a powerful tool, and as an alternative to conventional monitoring systems, allowing obtaining simultaneous spatial and temporal information within low thickness biofilms.
Esta tesis se centra en el desarrollo de nuevos microsensores diseñados específicamente para la monitorización de biopelículas y en su aplicación para el estudio y caracterización de biopelículas de diferente origen (heterótrofas y autótrofas). Utilizando tecnología de sistemas micro-electromecánicos se ha diseñado, fabricado y validado un microsensor amperométrico para la detección del oxígeno disuelto (OD), que mejora las prestaciones de los microsensores disponibles. El diseño multi-electrodo de este dispositivo permite obtener información simultánea de la concentración de OD en 8 puntos diferentes a lo largo de una biopelículas, con una excelente sensibilidad para la detección del OD y una elevada resolución espacial (<50 µm). La elevada robustez que presenta este tipo de dispositivos ha sido aprovechada para monitorizar biofiltros percoladores, obteniendo información a tiempo real de la concentración de OD en el interior de las biopelículas. La monitorización de las biopelículas heterótrofas ha servido para cuantificar en su interior las velocidades de transporte de materia. Estos resultados han sido utilizados para incrementar el conocimiento sobre los mecanismos que intervienen en estos procesos y para establecer la relación entre estos mecanismos, las condiciones hidrodinámicas del sistema y la estructura de la biopelícula. La información obtenida en estos estudios ha demostrado la importancia de incluir la heterogeneidad de las biopelículas en la descripción del transporte de materia, y ha sido utilizada para desarrollar dos correlaciones para la estimación de las velocidades de transporte de materia en el interior de las biopelículas estudiadas. La monitorización de biopelículas también se ha utilizado para desarrollar modelos cinéticos específicos para sustituir los modelos desarrollados en cultivos en suspensión, utilizados tradicionalmente para describir la actividad de biopelículas. A partir de la adquisición de perfiles de OD, H2S y pH en el interior de biopelículas ha sido posible calibrar modelos cinéticos que describen con precisión la actividad de microorganismos en el interior de biopelículas heterótrofas y sulfuroxidantes. Las medidas obtenidas con microsensores demostraron ser una excelente herramienta para validar los modelos de biofiltración y predecir con mayor precisión su comportamiento a partir de la caracterización del transporte de materia y la biocinética. Los resultados obtenidos en la simulación demostraron que la utilización de medidas directas en el interior de biopelículas, como elementos centrales del proceso biotecnológico, aumenta la rigurosidad de los modelos de biofiltración. La metodología desarrollada permitió diseñar un nuevo microsensor MEMS, basado en el de OD, que incorporó en un solo dispositivo la medida de OD y pH. El diseño y la fabricación del primer prototipo se modificaron para incluir una segunda matriz de electrodos para la detección potenciométrica del pH y para incorporar mejoras. La reducción de las dimensiones del microsensor y la protección de los electrodos hizo menos invasiva su medida y aumentó la estabilidad de su respuesta. Estas mejoras sitúan el microsensor como una herramienta de gran potencial, alternativa a los sistemas de monitorización convencionales, que permite obtener información simultánea espacial y temporal de la concentración de OD y pH en el interior de biopelículas con bajo grosor
Guimera, X.; Dorado, A.D.; Bonsfills, A.; Gabriel Buguña, Gemma; Gabriel, D.; Gamisans, X. Water research (Oxford) Vol. 102, p. 551-560 DOI: 10.1016/j.watres.2016.07.009 Data de publicació: 2016-07-07 Article en revista
Knowledge of mass transport mechanisms in biofilm-based technologies such as biofilters is essential to improve bioreactors performance by preventing mass transport limitation. External and internal mass transport in biofilms was characterized in heterotrophic biofilms grown on a flat plate bioreactor. Mass transport resistance through the liquid-biofilm interphase and diffusion within biofilms were quantified by in situ measurements using microsensors with a high spatial resolution (<50 mm). Experimental conditions were selected using a mathematical procedure based on the Fisher Information Matrix to increase the reliability of experimental data and minimize confidence intervals of estimated mass transport coefficients. The sensitivity of external and internal mass transport resistances to flow conditions within the range of typical fluid velocities over biofilms (Reynolds numbers between 0.5 and 7) was assessed. Estimated external mass transfer coefficients at different liquid phase flow velocities showed discrepancies with studies considering laminar conditions in the diffusive boundary layer near the liquid-biofilm interphase. The correlation of effective diffusivity with flow velocities showed that the heterogeneous structure of biofilms defines the transport mechanisms inside biofilms. Internal mass transport was driven by diffusion through cell clusters and aggregates at Re below 2.8. Conversely, mass transport was driven by advection within pores, voids and water channels at Re above 5.6. Between both flow velocities, mass transport occurred by a combination of advection and diffusion. Effective diffusivities estimated at different biofilm densities showed a linear increase of mass transport resistance due to a porosity decrease up to biofilm densities of 50 g VSS$L1. Mass transport was strongly limited at higher biofilm densities. Internal mass transport results were used to propose an empirical correlation to assess the effective diffusivity within biofilms considering the influence of hydrodynamics and biofilm density.
The oxidation of methane (CH4) using biofilters has been proposed as an alternative to mitigate anthropogenic greenhouse gas emissions with low concentration of CH4 that cannot be used as a source of energy. However conventional biofilters utilize organic packing materials that have a short lifetime, clogging problems and are commonly inoculated with non-specific microorganisms leading to unpredictable CH4 elimination capacities (EC) and removal efficiencies (RE). The main objective of this work was to characterize the oxidation of CH4 in two biotrickling filters (BTFs) packed with polyethylene rings and inoculated with two methanotrophic bacteria Methylomicrobium album and Methylocystis sp. in order to determine the CH4 elimination capacity (EC) and CO2 production (pCO2) when using a specific inoculum. The repeatability of the results in both BTF was determined when operated at the same inlet load of CH4.
Lopez, L.; Dorado, A.D.; Mora, M.; Gamisans, X.; Lafuente Sancho, Francisco Javier; Gabriel, D. Chemical engineering journal Vol. 294, p. 447-457 DOI: 10.1016/j.cej.2016.03.013 Data de publicació: 2016-06-15 Article en revista
A dynamic model describing physical-chemical and biological processes for the removal of high loads of H2S from biogas streams in biotrickling filters (BTFs) was developed, calibrated and validated for a wide range of experimental conditions in a lab-scale BTF. The model considers the main processes occurring in the three phases of a BTF (gas, liquid and biofilm) in a co-current flow mode configuration. Furthermore, this model attempts to describe accurately the intermediate (thiosulfate and elemental sulfur) and final products (sulfate) of H2S oxidation. A sensitivity analysis was performed in order to focus parameters estimation efforts on those parameters that showed the highest influence on the estimation of the H2S removal efficiency, the accumulated mass of sulfur and the sulfate concentration in the liquid phase. Biofilm and liquid layer thicknesses, specific growth rate of biomass over elemental sulfur and the H2S global mass transfer coefficient were the parameters that showed the highest influence on model outputs. Experimental data for model calibration corresponded to the operation of the BTF under stepwise increasing H2S concentrations between 2000 and 10,000 ppm(v). Once the model was calibrated, validation was performed by simulating a stationary feeding period of 42 days of operation of the BTF at an average concentration of 2000 ppm(v) and a dynamic operation period where the BTF was operated under variable inlet H2S concentration between 1000 and 5000 ppm(v) to simulate load fluctuations occurring in industrial facilities. The model described the reactor performance in terms of H2S removal and predicted satisfactorily the main intermediate and final products produced during the biological oxidation process.
Almenglo, F.; Ramírez, M.; Gómez, J.; Cantero, D.; Gamisans, X.; Dorado, A.D. Journal of chemical technology & biotechnology Vol. 91, num. 6, p. 1782-1793 DOI: 10.1002/jctb.4769 Data de publicació: 2016-06 Article en revista
A novel nanocomposite (NC) based on magnetite nanoparticles (Fe3O4-NPs) immobilized on the surface of a cationic exchange polymer, C100, using a modification of the co-precipitation method was developed to obtain magnetic NCs for phosphate removal and recovery from water. High-resolution transmission electron microscopy-energy-dispersive spectroscopy, scanning electron microscopy, X-ray diffraction, and inductively coupled plasma optical emission spectrometry were used to characterize the NCs. Continuous adsorption process by the so-called breakthrough curves was used to determine the adsorption capacity of the Fe3O4-based NC. The adsorption capacity conditions were studied under different conditions (pH, phosphate concentration, and concentration of nanoparticles). The optimum concentration of iron in the NC for phosphate removal was 23.59 mgFe/gNC. The sorption isotherms of this material were performed at pH 5 and 7. Taking into account the real application of this novel material in real water, the experiments were performed at pH 7, achieving an adsorption capacity higher than 4.9 mgPO4–P/gNC. Moreover, Freundlich, Langmuir, and a combination of them fit the experimental data and were used for interpreting the influence of pH on the sorption and the adsorption mechanism for this novel material. Furthermore, regeneration and reusability of the NC were tested, obtaining 97.5% recovery of phosphate for the first cycle, and at least seven cycles of adsorption–desorption were carried out with more than 40% of recovery. Thus, this work described a novel magnetic nanoadsorbent with properties for phosphate recovery in wastewater.
En este trabajo se presentan las herramientas desarrolladas por el grupo de investigación de la Universidad Politécnica de Cataluña en Manresa y colaboradores en el estudio de los bioprocesos para el tratamiento de corrientes gaseosas y olores, destacando entre ellas el uso de microsensores para la caracterización de biopelículas, la simulación del comportamiento hidrodinámico de los biorreactores para un diseño más preciso o el uso de configuraciones no convencionales, como los reactores de membrana, para superar las limitaciones actuales que presentan los bioprocesos clásicos. Con una elevada monitorización se evalúa durante un periodo continuado de 2 meses el comportamiento de una membrana biológica para la eliminación de compuestos volátiles que pudieran ser susceptibles de producir problemas de olores o problemas ambientales. Para conocer las limitaciones del sistema se desarrollan unos microsensores con elevada resolución espacial que permiten obtener información del interior de la biopelícula. Esta información es de gran utilidad para desarrollar modelos hidrodinámicos avanzados que permitan conocer mejor y optimizar los procesos biológicos para el tratamiento de gases y olores. Estos instrumentos de análisis avanzados pueden ser fácilmente adaptados a nuevas aplicaciones y su potencial de aplicación aún se encuentra en vías de desarrollo.
Two-phase partitioning bioreactors (TPPBs) are biological multiphase systems provided with a non-aqueous phase (NAP) with high affinity for target volatile organic compounds (VOCs). TPPBs have been particularly successful in the treatment of poorly-water soluble VOCs, supporting VOC removal at unprecedented rates and concentrations. Since experimental findings on mass transfer and pollutant uptake aspects have been reported during the last 10 years, the mathematical modeling of TPPBs is a research field that has evolved rapidly. In this work, a novel mathematical description of TPPBs, including continuous aqueous phase renewal and potential VOC uptake directly from the NAP, is presented. Stirred tank was used as a model system because most experimental data on TPPBs has been obtained in this bioreactor configuration. Model simulations indicated that TPPB performance can be enhanced by improving the partial mass transfer coefficient between the gas and the NAP. The model also showed that microorganisms with half-saturation constants < 5 g m-3 and ability to take up VOC directly from the NAP can boost significantly TPPB performance. The VOC removal efficiencies predicted by the model were significantly improved when VOC uptake from the NAP was assumed (up to 50% less relative error compared with simulations without this assumption). To the best of our knowledge, this is the first modeling platform for TPPBs considering continuous aqueous phase renewal and validated with experimental data for three VOCs without performing parameter fitting.
Prades, L.; Monrós-Andreu, G.; Dorado, A.D.; Chiva, S.; Gamisans, X. International Conference on Biotechniques for Air Pollution Control p. 434- Data de presentació: 2015-09-02 Presentació treball a congrés