El grup de recerca de tractament biològic de contaminants gasosos i olors de la UPC, ha esdevingut en els darrers anys un referent pel que fa a l’aplicació de tècniques biològiques per solucionar un ampli ventall de problemàtiques ambientals. Així, el grup ja posseeix una extensa experiència en l’ús de biofiltres pel tractament de diferents tipus de contaminants gasosos orgànics i inorgànics així com en la caracterització d’aquests dispositius tant des d’un punt de vista teòric (modelització avançada mitjançant tècniques CFD) com pràctic (disseny i construcció de plantes pilot, tècniques respiromètriques, monitoratge de biopel•lícules mitjançant microsensors dissenyats ad hoc, entre d’altres). El grup té àmplia experiència en la gestió de projectes públics i privats i, en general, en la transferència de coneixement. Recentment, el grup ha endegat una línia de recerca relacionada amb la recuperació de metalls valuosos de deixalles electròniques mitjançant microorganismes.
La empleabilidad es uno de los atractivos que aportan valor a los estudios de grado de las ingenierías. Este aspecto a menudo denostado en ambientes antisistema, en los últimos tiempos está recobrando importancia tras los efectos de la crisis experimentada estos últimos años y gana influencia en los parámetros a considerar al establecer los ranquings universitarios (ranking QS).
En este sentido la UPC de Manresa está planeando la captación de estudiantes en el grado de ingeniería química a partir del programa talento en la ingeniería química para la Cataluña central, en el cual se ofrece como ingrediente destacado la experiencia de ingenieros que trabajan en la industria como vínculo para captar el interés de ellos.
En las sesiones del programa (de una duración de 6 horas, una de las horas se dedica a una sesión de speed networking donde los estudiantes en grupos de hasta 6 personas preguntan discrecionalmente a los ingenieros sobre su experiencia laboral. Ello permite introducir aspectos de carácter práctico que aunque podrían alejar al bachiller de la imagen idílica de una carrera, creemos que los acerca a un aspecto real de su futuro como ciudadanos con una responsabilidad respecto a la profesión a elegir.
El present informe s'ha emes per tal de donar compliment a l'encàrrec realitzat per Casals Cardona Industrial S.A. en relació al projecte de determinació de compostos orgànics volàtils de !'empresa PEINAJE DEL RIO LLOBREGAT ubicada a Ctra d'Artés, s/n. (B-451) 08272 SANT FRUITÓS DE BAGES.
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.
Els incendis forestals són consubstancials al clima i la vegetació mediterrània. L’existència d’una massa forestal de l’ordre del 60% a Catalunya i l’increment d’aquesta conjuntament amb la seva escassa gestió forestal han propiciat el creixement d’episodis d’incendis forestals. A més s’hi s’afegeix el creixement d’episodis climàtics extrems deguts al canvi climàtic induït per l’increment del CO2 base de l’era industrial. El clima mediterrani està associat a un règim hidrogràfic en el qual sequeres i aiguats han incrementat la seva freqüència.
La present comunicació pretén exemplificar aquest tret característic de la Catalunya central a las darreres dècades, a partir del mostreig de les aigües de la conca hidrogràfica del Llobregat en episodis d’incendis forestals. Tot i la possible incidència d’aquests episodis en la salut humana a través de l‘aparició de concentracions elevades d’hidrocarburs aromàtics policíclics (HAPs) coneguts components carcinògens d’aigües contaminades. Aquestes no han representat un problema sanitari en la captació d’aigües per al consum humà ja que en els estudis descrits aquestes no sobrepassaren llindars perillosos per a la salut humana en base als paràmetres establerts per la legislació europea.
En aquesta comunicació es mesuren les concentracions d’hidrocarburs aromàtics policíclics mesurades en el sistema fluvial del Llobregat a les comarques del Bages nord. Aquests compostos foren extrets de les aigües mostrejades mitjançant extracció amb dissolvents orgànics i fraccionament per cromatografia. Posteriorment foren analitzats mitjançant la tècnica de cromatografia de gasos acoblada a l’espectrometria de masses així com quantificades emprant el mètode del patró intern.
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.
Escobet, A.; Nebot, M.; Mugica, F.; Gamisans, X.; Guimera, X. International Conference on Simulation and Modeling Methodologies, Technologies and Applications p. 458-465 Data de presentació: 2017-07-27 Presentació treball a congrés
Sulfur oxides are some of the major existing pollutants that directly affect the atmosphere. In combination with particles and air humidity, produce the most detrimental effects attributed to air pollution. The treatment of gas streams containing sulfur dioxide and its subsequent recovery is, therefore, a matter of great importance for the elimination of the environmental burden of their emission into the atmosphere. In this research, a fuzzy model of a flue-gas desulfurization plant is developed with the aim of dealing with two optimizations problems. The first one, is centered in finding the amount of liquid that should be injected into the plant in order to optimize the SO2 absorption process. The second one, is the development of a tool to help to size the
absorption tower (find the right dimension), given the optimum amount of liquid derived from the previous goal. The results obtained, although preliminary, are reliable and useful for chemical engineering plant design.
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.