Catalytic azo dye reduction in advanced anaerobic bioreactors

En un reactor anaeróbico de lecho empacado y de flujo ascendente con carbón activado (AC) biológico se obtuvieron altas velocidades de conversión del colorante azoico Acid Orange 7 a tiempos espaciales muy cortos, hasta 99% en 2.0 min. Tanto el área superficial específica como la conductividad electrónica del AC contribuyeron a las mayores velocidades de reducción. La agitación en el lecho de carbón produjo un incremento de la bioconversión del colorante. Se estableció un modelo cinético de decoloración que implica catálisis heterogénea y bioreducción. La biodegradabilidad anaeróbica de un colorante azoico en el sistema reactivo agitado pudo ser predicha a partir de su potencial de reducción. Las velocidades de decoloración fueron significativamente influenciadas por las propiedades texturales del AC y moderadamente afectadas por su química superficial. Este bioreactor catalítico parece ser una alternativa atractiva para la mejora económica de las tecnologías de tratamiento de aguas residuales textiles y de colorantes.In an anaerobic upflow packed-bed reactor with biological activated carbon (AC), high azo dye Acid Orange 7 conversion rates were achieved during very short space times up to 99% in 2.0 min. Both electron conductivity and specific surface area of AC contributed to higher reduction rates. The application of stirring in the carbon bed resulted in an increase of dye bioconversion. A decolourisation model was developed involving both heterogeneous catalysis and bioreduction. The anaerobic biodegradability of an azo dye could be predicted by its reduction potential in the stirred reactor system. The decolourisation rates were found to be significantly influenced by the textural properties of AC and moderately affected by its surface chemistry. This catalytic bioreactor system seems to be an attractive alternative for economically improving textile/dye wastewater technologies

Novel magnetically induced membrane vibration (MMV) for fouling control in membrane bioreactors

Conventional submerged membrane bioreactors (MBRs) rely on the coarse bubbles aeration to generate shear at the liquid membrane interface to limit membrane fouling. Unfortunately, it is a very energy consuming method, still often resulting in a rapid decrease of membrane permeability and consequently in higher expenses. In this paper, the feasibility of a novel magnetically induced membrane vibration (MMV) system was studied in a labscale MBR treating synthetic wastewater. The effects on membrane fouling of applied electrical power of different operation strategies, of membrane flux and of the presence of multiple membranes on one vibrating engine on membrane fouling were investigated. The filtration performance was evaluated by determining the filtration resistance profiles and critical flux. The results showed clear advantages of the vibrating system over conventional MBR processes by ensuring higher fluxes at lower fouling rates. Intermittent vibration was found a promising strategy for both efficient fouling control and significant energy saving. The optimised MMV system is presumed to lead to significant energy and cost reduction in up-scaled MBR operations. (C) 2011 Elsevier Ltd. All rights reserved.status: publishe

Texture-modified activated carbons as catalysts in biodecolourisation of azo dyes

Considerable attention has been focused on the reduction of azo dyes discharged from dyeing, textile and other industries since some of them or their metabolites may cause toxicity. The efficient treatment of these effluents at industrual scale presents many difficulties, particularly at high dye concentrations and at low energy consumptions. Anaerobic biodecolourisation seems to be the most economic and environmentally friendly method for azo dye wastewater treatment. In a recent study of the authors1, a novel-type bioreactor with activated carbon (AC) was developed providing high azo dye degradation rates at very short space times/hydraulic residence times. Additionally, a model was proposed involving both heterogeneous catalysis and biological decolourisation. In catalysis, activated carbons have been mainly used as support, but their use as catalysts on their own is growing quickly. One of the advantages of ACs is the possibility of tailoring their physical and/or chemical properties in order to optimise their performance for specific applications.2 Therefore, it is important to analyse the effect of texture and surface chemistry of AC in azo dye degradation by using ACs with diverse average pore sizes and/or surface chemistries in the bioreactors. This work deals with texture-modified activated carbons for the decolourisation of azo dyes in upflow stirred packed-bed reactors (USPBRs) containing a biological activated carbon system. The preparation, modification and characterisation of pore size-modified activated carbons have been completed. The initial material selected was a commercial activated carbon (Norit Rox 0.8). ACs with larger porosities were obtained by CO2 gasification of the raw carbon previously impregnated with cobalt. The role of cobalt was to catalyse the gasification of carbon, thereby promoting the formation of mesopores. The gasification experiments were carried out in a tubular vertical reactor. ACs with different average pore sizes were produced by applying different gasification times. The textural characterisation was based on N2 adsorption isotherms at 77 K. The performance of these carbons on azo dye biodegradation in the USPBRs is being evaluated

Texture-modified activated carbons as catalysts in biodecolourisation of azo dyes

Considerable attention has been focused on the reduction of azo dyes discharged from dyeing, textile and other industries since some of them or their metabolites may cause toxicity. The efficient treatment of these effluents at industrual scale presents many difficulties, particularly at high dye concentrations and at low energy consumptions. Anaerobic biodecolourisation seems to be the most economic and environmentally friendly method for azo dye wastewater treatment. In a recent study of the authors1, a novel-type bioreactor with activated carbon (AC) was developed providing high azo dye degradation rates at very short space times/hydraulic residence times. Additionally, a model was proposed involving both heterogeneous catalysis and biological decolourisation. In catalysis, activated carbons have been mainly used as support, but their use as catalysts on their own is growing quickly. One of the advantages of ACs is the possibility of tailoring their physical and/or chemical properties in order to optimise their performance for specific applications.2 Therefore, it is important to analyse the effect of texture and surface chemistry of AC in azo dye degradation by using ACs with diverse average pore sizes and/or surface chemistries in the bioreactors. This work deals with texture-modified activated carbons for the decolourisation of azo dyes in upflow stirred packed-bed reactors (USPBRs) containing a biological activated carbon system. The preparation, modification and characterisation of pore size-modified activated carbons have been completed. The initial material selected was a commercial activated carbon (Norit Rox 0.8). ACs with larger porosities were obtained by CO2 gasification of the raw carbon previously impregnated with cobalt. The role of cobalt was to catalyse the gasification of carbon, thereby promoting the formation of mesopores. The gasification experiments were carried out in a tubular vertical reactor. ACs with different average pore sizes were produced by applying different gasification times. The textural characterisation was based on N2 adsorption isotherms at 77 K. The performance of these carbons on azo dye biodegradation in the USPBRs is being evaluated

Texture-modified activated carbons as catalysts in biodecolourisation of azo dyes

Considerable attention has been focused on the reduction of azo dyes discharged from dyeing, textile and other industries since some of them or their metabolites may cause toxicity. The efficient treatment of these effluents at industrual scale presents many difficulties, particularly at high dye concentrations and at low energy consumptions. Anaerobic biodecolourisation seems to be the most economic and environmentally friendly method for azo dye wastewater treatment. In a recent study of the authors1, a novel-type bioreactor with activated carbon (AC) was developed providing high azo dye degradation rates at very short space times/hydraulic residence times. Additionally, a model was proposed involving both heterogeneous catalysis and biological decolourisation. In catalysis, activated carbons have been mainly used as support, but their use as catalysts on their own is growing quickly. One of the advantages of ACs is the possibility of tailoring their physical and/or chemical properties in order to optimise their performance for specific applications.2 Therefore, it is important to analyse the effect of texture and surface chemistry of AC in azo dye degradation by using ACs with diverse average pore sizes and/or surface chemistries in the bioreactors. This work deals with texture-modified activated carbons for the decolourisation of azo dyes in upflow stirred packed-bed reactors (USPBRs) containing a biological activated carbon system. The preparation, modification and characterisation of pore size-modified activated carbons have been completed. The initial material selected was a commercial activated carbon (Norit Rox 0.8). ACs with larger porosities were obtained by CO2 gasification of the raw carbon previously impregnated with cobalt. The role of cobalt was to catalyse the gasification of carbon, thereby promoting the formation of mesopores. The gasification experiments were carried out in a tubular vertical reactor. ACs with different average pore sizes were produced by applying different gasification times. The textural characterisation was based on N2 adsorption isotherms at 77 K. The performance of these carbons on azo dye biodegradation in the USPBRs is being evaluated.Postprint (published version