Modelling of the biofiltration of reduced sulphur compounds through biotrickling filters connected in series: Effect of H2S

Background: The behaviour of two biotrickling filters connected in serie (BTF) inoculated with Acidithiobacillus thiooxidans and Thiobacillus thioparus , biodegrading hydrogen sulphide (H2S) and dimethyl sulphide (DMS) simultaneously were studied. A model which considers gas to liquid mass transfer and biooxidation in the biofilm attached to the support is developed. Additionally, a fixed bed biotrickling filter where the microorganism is immobilized in a biofilm which degrades a mixture of H2S and DMS is implemented. Validation of the model was carried out using experimental data obtained at different H2S and DMS loads. Results: The inhibitory effect caused by the presence of H2S on the DMS is observed, which is evidenced by the decrease of the DMS removal efficiency from 80 to 27%, due to the preference that T. thioparus has by simple metabolism. H2S is not affected by the DMS, with removal efficiencies of 95 to 97%, but it decreases at high concentrations of the compound, due to the inhibition of metabolism by high H2S input loads. The model which describes the BFT fits successfully with the experimental results and it has a high sensitivity to inhibition parameters. Conclusions: It is shown that the microorganism has a high affinity for H2S, producing substrate inhibition when the concentration is high. The H2S is able to inhibit the DMS biooxidation, whereas the DMS does not affect the H2S biooxidation

Coupling composting and biofiltration for ammonia and volatile organic compounds removal

The efficiency of a compost biofilter for the simultaneous removal of ammonia and volatile organic compounds (VOCs) from exhaust gases of the composting process of different organic wastes (source-selected organic fraction of municipal solid wastes and animal by-products) is studied. An average ammonia removal efficiency of 94.7% was obtained in the biofilter for an average loading rate range of 846-to 67100 mg [NH3] m⁻³ biofilter h⁻¹. However, a sharp reduction in NH3 removal was observed when the waste gas contained a high, more than 2000 mg m⁻³, NH3 concentration. The maximum VOC removal efficiency was 82% when the biofilter worked at a loading rate range of 0.55-28.8 g [C] m⁻³ biofilter h⁻¹

Avaliação de bactérias provenientes de um biofiltro de tratamento de vapores de gasolina

Dissertaçao (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Ambiental.Em todo o mundo a preocupação em relação à poluição atmosférica é crescente, mais especificamente com relação à contaminação por substâncias com características de toxicidade e persistência que as tornam perigosas à saúde humana, às plantas e aos animais. A indústria do petróleo e o uso de seus derivados contribuem significativamente na liberação dos compostos orgânicos voláteis. A problemática ambiental da presença de compostos voláteis na atmosfera deve-se ao fato de alguns serem tóxicos, apresentarem forte odor e estarem envolvidos com chuva ácida, smog fotoquímico e efeito estufa. Os tanques de gasolina representam uma grande fonte de emissões atmosféricas, com perdas de 65,64 t.ano-1. O vapor da gasolina consiste em uma mistura de aproximadamente 90 hidrocarbonetos voláteis, incluindo cadeias alifáticas, cicloalcanos e aromáticos. Devido ao problema ambiental desses poluentes, torna-se necessário medidas de redução e tratamento, tanto por métodos físicoquímico quanto por biológicos. A biofiltração é apondada pela EPA como a melhor tecnologia para tratamento de vapores de gasolina emanados de postos de combustíveis e liberados pelos solos contaminados. Essa tecnologia é baseada na transferência do gás para uma fase líquida dentro de um meio suporte contendo microrganismos, onde ocorrerá a oxidação do poluente liberando CO2 e H2O. Este trabalho teve como objetivo isolar microrganismos provenientes de um biofiltro utilizado para tratamento de vapores de gasolina, estudar a abundância, morfologia e avaliar o crescimento utilizando gasolina como fonte de carbono e energia. Foi realizada a contagem das UFC/g, a avaliação do crescimento em meio líquido com diferentes concentrações de gasolina, a produção de biosurfactantes e a determinação para três bactérias com diferentes habilidades na utilização do substrato. Os resultados mostraram que a microbiota predominate em biofiltros de tratamento de vapores de gasolina é Gram negativa, apresentando contagem da ordem de 1,8x107 UFC/g, o que é coerente para esses sistemas. Também foi verificado que nem todos os isolados que utilizam de alguma forma a gasolina são capazes de produzir biosurfactantes. Entretanto, observou-se uma relação positiva entre a produção de biosurfactantes e o crescimento bacteriano. A presença de bactérias na amostra do suporte do biofiltro que isoladamente não cresceram na presença de gasolina sugere uma co-relação inter-específica com bactérias degradadoras de gasolina. Concentrações de gasolina da ordem de 0,2 % e superiores são tóxicas para micorganismos isolados de zonas do biofiltro que operam com baixas concentrações de vapores de gasolina. Os isolados produtores de biosurfactante apresentam maior crescimento, representando um potencial maior para utilização como inoculantes para sistemas de tratamento de vapores de gasolina

Treatment of volatile organic compounds by biofiltration with and without percolation : kinetic and characterization studies

The objectives of this work are related to the kinetic study and characterization of air treatment biofilters with and without percolation which were packed with inert packing materials in order to treat methanol, ethanol and toluene vapours.The thesis is divided into three sections.The first section contains a bibliographic introduction to biofiltration and an experimental study.The review of experimental work shows that methanol, ethanol and toluene can be treated in biofilters with or without percolation. In the experimental study of this section, ethanol is treated in a biotrickling filter at low nitrogen concentrations in the nutrient solution and high removal efficiencies are obtained. In this study, experimental protocols for maintaining the biofilter and controlling the biomass content in the packing bed were developed.The second section is composed of two experimental studies for characterizing biofilters with and without percolation in order to treat methanol. A methodology for calculating the biomass accumulated in the packing bed of a biofilter is among the new experimental protocols developed in this study. In the case of biotrickling filter, methodologies for determining the partition coefficient of methanol and the biomass production rate were developed.The role of the biofilm and the nutrient solution on bioflter performance was also analyzed.The studies of this section lead to a better comprehension of methanol biodegradation in biofilters.The third section contains two kinetic studies for biofilters with and without percolation. In the first study, a new experimental methodology is proposed to calculate microkinetic parameters related to microbial growth in a biofilter. In the second study, the microkinetic and macrokinetic behaviors of methanol and toluene biodegradation are compared.The influence of operating conditions on microbial growth and elimination capacity is also analyzed. This study includes the identification of energy indicators of biofilters with and without percolation, which could be used in energy balances and for estimating the temperature of packing bed

Aplicação da biofiltração no tratamento de vapores de gasolina /

Orientadora : Profª Drª Adenise Lorenci WoiciechowskiOrientador : Carlos Ricardo SoccolTese (doutorado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduaçao em Processos Biotecnológicos. Defesa: Curitiba, 2006Inclui bibliografiaÁrea de concentração: Saude humana e anima

Modelación del proceso de biofiltro percolador para el tratamiento de emisiones en aire de Compuestos Orgánicos Volátiles de elevada solubilidad en agua

La contaminación del aire producida por las emisiones a la atmosfera de compuestos orgánicos volátiles (COV) es una de las causas más importantes asociadas al deterioro de la calidad ambiental. Una de las fuentes principales de emisión de COV son las industrias que utilizan disolventes. En este sentido, las industrias deben hacer un esfuerzo por adaptar sus procesos productivos para minimizar el impacto ambiental. Sin embargo, las propiedades de los disolventes los convierten en indispensables en algunas aplicaciones por lo que el tratamiento de las emisiones derivadas de su uso se convierte en una necesidad. El uso de biofiltros percoladores para la depuración de COV de elevada solubilidad en agua es una tecnología sostenible, habiéndose demostrado que es una alternativa viable técnica y económicamente, tal y como avalan las investigaciones realizadas en las últimas décadas. Sin embargo, el desarrollo de la investigación sobre esta tecnología requiere dar un paso más para lograr consolidarla en el entorno industrial. Este trabajo de tesis doctoral tiene como objetivo principal el de desarrollar una herramienta matemática que incluya los principales mecanismos involucrados en la depuración de aire contaminado con COV de elevada solubilidad en agua mediante el proceso de biofiltro percolador en condiciones de operación típicas de la industria. Los COV de elevada solubilidad en agua están presentes de manera habitual en las emisiones gaseosas procedentes de la industria entre otras, de impresión flexográfica. Pese a que son compuestos con una biodegradabilidad relativamente elevada, la depuración de este tipo de COV suele verse limitada por la disponibilidad de oxígeno en el interior de la biopelícula, lo que favorece la acumulación de contaminante en el interior del sistema. En este sentido, una parte importante de la tesis doctoral ha consistido en profundizar en los mecanismos de transferencia de materia de contaminante y de oxígeno mediante la determinación de los coeficientes de transferencia de materia para ambos compuestos. La herramienta matemática desarrollada en la presente tesis doctoral tiene como finalidad simular y predecir la respuesta transitoria de los biofiltros percoladores sometidos a condiciones de carga variable y riego intermitente. El modelo matemático ha sido aplicado tanto a biofiltros percoladores utilizados en el laboratorio, en condiciones controladas de operación, como a biofiltros percoladores situados en instalaciones industriales, en los que se suele observar patrones de emisión más amortiguados. En la primera etapa de este trabajo se llevó a cabo el estudio experimental a escala de laboratorio de eliminación de emisiones en aire que contenían isopropanol, elegido éste como contaminante modelo. Para ello se utilizaron dos biofiltros percoladores empaquetados con diferente material de relleno: uno desordenado y otro estructurado. Durante este estudio se sometieron a los reactores a condiciones discontinuas de alimentación y de riego intermitente, y se evaluó la respuesta del biofiltro percolador a cambios en la concentración de alimentación de contaminante y de caudal de gas. Los resultados indicaron que el uso de patrones de riego intermitente provocaba una emisión fugitiva de contaminante en la corriente gaseosa de salida del biofiltro percolador que coincidía con el momento del riego. Para evaluar este efecto se aplicaron diferentes condiciones de riego al sistema, concluyendo que el patrón de riego podía utilizarse como estrategia para aumentar el rendimiento del reactor. Así mismo se sometió al reactor a un periodo de 7 semanas sin alimentación de COV. La capacidad de recuperación de los biofiltros percoladores puso de manifiesto la robustez del sistema. La siguiente fase de la tesis se centró en el estudio de la transferencia de materia en los biofiltros percoladores. Para ello se determinaron los coeficientes de transferencia de materia de isopropanol y de oxígeno para diferentes velocidades superficiales de líquido y de gas y para varios materiales de relleno. Los datos obtenidos en este estudio permitieron desarrollar correlaciones empíricas para caracterizar la relación entre los coeficientes de transferencia de materia y las velocidades superficiales de gas y de líquido aplicadas en el biofiltro percolador. Así mismo, se evaluó un material de relleno de uso industrial en términos de transferencia de oxígeno con el objetivo de compararlo con los materiales de relleno empleados en el laboratorio, demostrándose que, en las velocidades de aplicación de los biofiltros percoladores industriales, la transferencia de oxígeno para este material era similar a la obtenida con los materiales utilizados en el laboratorio. En la última parte del presente estudio se desarrolló un modelo matemático para la predicción de la respuesta transitoria de los biofiltros percoladores en condiciones de estado no estacionario de carga y de riego intermitente. El desarrollo del modelo se basó en balances de materia de isopropanol y de oxígeno en la fase gas, en la fase líquida y en la biopelícula. El modelo matemático se desarrolló asumiendo condiciones cíclicas de periodos con riego y de periodos sin riego, ya que ésta es la forma habitual de operación a nivel industrial. Durante los periodos con riego se consideró una fase líquida móvil, mientras que durante los periodos sin riego se consideró una fase líquida estancada. La calibración y validación del modelo matemático se realizó con datos de biofiltros percoladores utilizados a escala de laboratorio y a escala industrial. Las principales hipótesis del modelo estuvieron relacionadas con la resistencia a la transferencia de materia tanto durante el riego (fase líquida móvil) como durante el no riego (fase líquida estancada). La calibración del modelo se llevó a cabo con datos de experimentos realizados a escala de laboratorio en biofiltros percoladores sometidos a riego discontinuo y carga de contaminante intermitente. Considerando despreciable la resistencia a la transferencia de materia producida por la fase líquida estancada durante los periodos sin riego, el modelo fue capaz de reproducir el rendimiento global del sistema así como el patrón de emisiones ocasionado por el riego discontinuo. Además, permitió identificar que la relación entre la concentración de carbono orgánico en el tanque de recirculación y la emisión fugitiva observada durante los periodos con riego estaba asociada al incremento de la resistencia a la transferencia de materia entre la fase gas y la fase líquida móvil con respecto a las determinaciones realizadas en condiciones abióticas. Este fenómeno se asoció al cambio de las propiedades físicas que ocasiona la presencia de biopelícula. La aplicación del modelo para la predicción de las emisiones de salida de un biofiltro percolador instalado en una industria de impresión flexográfica demostró la utilidad práctica del modelo. La aplicación del modelo para la simulación de esta corriente se basó en las hipótesis de la existencia de una resistencia a la transferencia de materia de la fase gas a la fase líquida móvil durante el riego y una resistencia adicional con respecto al biofiltro percolador de laboratorio a la transferencia de materia desde la fase gas a la fase líquida estancada durante los periodos sin riego. Se utilizó un mayor espesor de biopelícula que en los biofiltros percoladores empleados en el laboratorio ya que se identificó que ésta actuaba cíclicamente como fuente/sumidero asociado a los periodos diarios de fabricación/no fabricación. El elevado espesor de la biopelícula provocó que durante los periodos de alimentación de COV al sistema, la parte no degradada del contaminante se acumulara en la biopelícula, produciéndose su desorción en los periodos en los que circulaba aire limpio por el reactor. Todo ello demostró la capacidad del modelo para reproducir los fenómenos complejos involucrados en la respuesta dinámica de los biofiltros percoladores que tratan compuestos orgánicos volátiles de elevada solubilidad en agua. El modelo matemático se integró en una herramienta informática mediante una GUI (Graphical User Inteface) desarrollada con MATLAB®. A fin de facilitar la comunicación con el usuario final, se generaron dos interfaces: una interfaz para introducir los datos para realizar las simulaciones y una interfaz de resultados. La herramienta desarrollada permite introducir de una manera sencilla patrones de concentraciones y caudales de gas variables, así como el uso de patrones de riego intermitente. Al terminar la simulación, la herramienta ofrece una pantalla de resultados con la información más relevante para evaluar el funcionamiento de los biofiltros percoladores: gráficas de patrón de emisión de la concentración de contaminante en la fase gas a la entrada y a la salida del reactor y de la variación temporal de la concentración de carbono disuelto en el tanque de recirculación, así como datos promedio de concentración de contaminante en las emisiones gaseosas a la entrada y a la salida del bioreactor, de carga volumétrica y de capacidad de eliminación.Air pollution produced by the emission to the atmosphere of volatile organic compounds (VOCs) is one of the most important causes associated with deterioration of air quality. One of the main sources of VOC emissions are companies that use solvents. In this regard, they should make an effort to adapt their production processes in order to minimise environmental impact. However, the properties of solvents make them essential in certain applications, so the treatment of derivative emissions becomes a necessity. Use of biotrickling filters for the removal of highly water soluble VOCs is a sustainable technology, having been proven to be technologically and economically a viable alternative, as supported by research in the last few decades. However, research development on this technology requires one further step to achieve consolidation in the industrial environment. The main objective of this dissertation is to develop a mathematical tool that includes the principal mechanisms involved in the removal of VOCs of high solubility in water from air emissions by the biotrickling filtration process in typical industry operating conditions. VOCs of high solubility in water are usually present in gaseous emissions from the flexographic printing industry, among others. Despite being compounds with a relatively high biodegradability, biological removal of such compounds is often limited by oxygen availability within biofilm, which leads to pollutant accumulation within the system. In this regard, an important part of the thesis was focused on the study of the mechanisms of mass transfer of pollutants and oxygen by means of the determination of the mass transfer coefficients for both compounds. The mathematical tool developed here aims to simulate and predict the transient response of the biotrickling filters under variable loading conditions and intermittent spraying. The mathematical model has been applied to biotrickling filters used in the laboratory, under controlled operating conditions, as well as to biotrickling filters located in industrial facilities, in which more buffered emission patterns are observed. The first stage of this work comprises the removal of isopropanol in air emissions at the laboratory scale, selected as a model pollutant. For this purpose, two biotrickling filters filled with different packing materials were used: a random one and a structured one. The reactors were operated under discontinuous loading conditions and intermittent spraying. The response of the biotrickling filter to variations in the inlet concentration of pollutant, as well as in the gas flow, was evaluated. The results showed that intermittent spraying caused a fugitive pollutant emission in the outlet gaseous stream of the biotrickling during spraying. To evaluate this effect, different spraying conditions were tested, concluding that the spray pattern could be used as a strategy to increase the reactor performance. Likewise, a starvation period of seven weeks was applied to both reactors. The resilience of the biotrickling filters showed the robustness of the system. The next stage was focused on the study of mass transfer in biotrickling filters. For this purpose, the mass transfer coefficients of oxygen and of isopropanol were determined. Different superficial gas and liquid velocities as well as different packing materials were tested. Results allowed empirical correlations to be established, which characterised the relationship between the mass transfer coefficients and superficial velocities of liquid and of gas applied to the biotrickling filters. Likewise, a packing material for industrial use was evaluated in terms of oxygen mass transfer, in order to compare it to the packing materials applied in the laboratory. At typical industrial operating conditions, oxygen mass transfer for the industrial material was found to be similar to those obtained for the laboratory packing materials. In the final stage, a mathematical model was developed in order to predict the transient response of the biotrickling filters under non-steady conditions of pollutant loading and of intermittent spray. The model development was based on the mass balances of isopropanol and of oxygen in the gas phase, in the liquid phase and in the biofilm. The mathematical model was built assuming cyclic conditions of spraying/non-spraying periods, the common industrial operational protocol. During spraying periods, a mobile liquid phase was considered, while during non-spraying periods, a stagnant liquid phase was considered. The calibration and validation of the mathematical model was performed using data from biotrickling filters operated at laboratory and industrial scales. The main hypotheses of the model were related to mass transfer resistance during spraying (mobile liquid phase) and mass transfer resistance during non-spraying (stagnant liquid phase). Model calibration was carried out with laboratory biotrickling filters operated under discontinuous spraying and intermittent pollutant loading. By assuming negligible mass transfer resistance for the stagnant liquid phase during non-spraying, the model was able to reproduce the average system performance and the emission pattern occasioned by the discontinuous spraying. In addition, the relationship between VOC concentration in the recirculation tank and the fugitive emission observed during spraying periods was related to higher mass transfer resistance between the gas and the mobile liquid phase during spraying than that obtained during abiotic determinations. This phenomenon was associated with variations in the physical properties caused by the presence of biofilm. The model application for predicting outlet emissions of a biotrickling filter installed in the flexographic printing industrial facility demonstrated its practical usefulness. Model application for simulating this industrial air flow was based on the hypotheses of mass transfer resistance for the mobile liquid phase during spraying and an additional mass transfer resistance from the stagnant liquid phase during non-spraying with respect to laboratory experiments. It was identified that the biofilm acted as a source/sink associated with daily periods of manufacturing/ non-manufacturing. Thus, a greater thickness of biofilm than in the laboratory biotrickling filters was fixed. The thick biofilm caused the accumulation of the non-degraded pollutant during periods with VOCs feeding to the system. The stored pollutant in the biofilm led to desorption during periods when clean air circulated through the reactor. The model capability to reproduce the complex phenomena involved in the dynamic response of the biotrickling filters treating volatile organic compounds with high water solubility was demonstrated. The mathematical model was integrated into an informatics tool using a GUI (Graphical User Interface) developed with MATLAB®. In order to facilitate communication with the end user, two interfaces were generated: an interface to enter data for simulations, and a results interface. The developed tool allows for the introduction of variable patterns of concentration and gas flows in a simple way, and also the use of intermittent spraying patterns. When the simulation ends, the tool offers a results screen with the most relevant information to evaluate the performance of the biotrickling filters: graphic information regarding the pattern of the gaseous emissions at the inlet and at the outlet of the reactor, as well as graphic information regarding the variation of dissolved organic carbon in the recirculation tank. Average data regarding the concentration in the gaseous emission at the inlet and at the outlet of the bioreactor, and the inlet load and the elimination capacity, are also provided