Revista Internacional de Contaminación Ambiental
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Indicadores de la bioeconomía circular para el aprovechamiento de la fracción orgánica de los residuos sólidos urbanos
Get PDFFor a sustainable development it is necessary to promote the actions inherent to circular economy (CE), such as the proper management and use of municipal solid waste (MSW) including its organic fraction (OFMSW) to obtain products with commercial relevance. Nonetheless, the criteria and metrics to evaluate circularity of products and processes present a variety of forms and references, and in some cases, they lack a clear methodological framework that allows to apply them in a concrete way in circular bioeconomy (CBE), what means the treatment of materials of biological origin through bioprocesses. In this work, we critically reviewed the published indicators that are used to evaluate the CE processes to collect the appropriate indicators for their application in circular bioeconomy systems, particularly those that involve the treatment of the OFMSW. These indicators can be quantitative or qualitative and provide decision makers with elements on economics, environment, society, and productive efficiency aspects. The group of selected indicators from our review process consists of 17 metrics and indicators that were chosen regarding the relevance of the variables they involve and their potential for application to OFMSW treatment bioprocesses. This study is a contribution to the organization of the existing technical information on this type of indicators and provides useful information for a conceptual framework that fosters the progress of the circular bioeconomy and its application to OFMSW.Para el desarrollo sostenible es necesario impulsar acciones inherentes a la economía circular (EC), como el manejo y aprovechamiento de los residuos sólidos urbanos (RSU), incluyendo su fracción orgánica (FORSU) para la obtención de productos de interés comercial. Sin embargo, los criterios y métricas para evaluar la circularidad de los procesos presentan una variedad de formas y referencias y en algunos casos carecen de un marco metodológico claro que permita aplicarlos de forma concreta en los procesos de la bioeconomía circular (BEC), es decir, aquellos que se centran en la gestión de materiales de origen biológico a través de bioprocesos. En este trabajo se propuso revisar críticamente los indicadores publicados para evaluar los procesos de EC, con la finalidad de proponer los más adecuados para su aplicación en sistemas de bioeconomía circular, particularmente en aquellos que involucran el tratamiento de la FORSU. Estos indicadores pueden ser cuantitativos o cualitativos y permiten hacerse de elementos para tomar decisiones económicas, ambientales, sociales y de eficiencia productiva. El conjunto de indicadores propuesto para la evaluación de la circularidad se basó en una revisión crítica para la selección final de 17 métricas e indicadores por la pertinencia de las variables que involucran y su potencial de aplicación a los bioprocesos de tratamiento de la FORSU. Este estudio es relevante porque proporciona información útil para la conformación de un marco conceptual que favorezca el progreso de la bioeconomía circular y su aplicación en la gestión de la FORSU
Improving tactile ground surface indicators based on fuzzy-AHP method: The case of Gulou District, Nanjing, China
Get PDFThere are many problems in the practical use of tactile ground surface indicators (TGSIs), and the large amount of TGSI construction currently being carried out does not always have a beneficial impact on the travel of visually impaired groups. Taking the roadside pedestrian space in the Gulou District of Nanjing City as an example, this paper established a TGSI quality evaluation system including six first-level indicators and 24 second-level indicators. The analytic hierarchy process (AHP) was used to determine the weight of the indicators at all levels, and evaluate six urban main roads, six urban secondary main roads and six sidewalks beside access roads, which were selected randomly. Visually impaired people were then asked to evaluate the TGSIs in the pedestrian spaces along these roads. Statistical analysis and evaluation showed that the indicators used in the evaluation system were satisfactory. The evaluation results revealed problems with the standardization, safety, accessibility, continuity, comfort and aesthetics of TGSIs in the urban roadside pedestrian space of Gulou. Analysis of the combined data showed that travel conditions for the visually impaired are currently worse in the old city area than in the new city area and that they are worse in low-grade pedestrian space than along high-grade roads. In order to solve these problems, strategies are put forward for improving the quality of TGSIs in the pedestrian space of Nanjing’s Gulou District in four aspects: improving TGSI structure, optimizing TGSI location, improving the TGSI system, and adapting TGSI implementation according to local conditions.There are many problems in the practical use of tactile ground surface indicators (TGSIs), and the large amount of TGSI construction currently being carried out does not always have a beneficial impact on the travel of visually impaired groups. Taking the roadside pedestrian space in the Gulou District of Nanjing City as an example, this paper established a TGSI quality evaluation system including six first-level indicators and 24 second-level indicators. The analytic hierarchy process (AHP) was used to determine the weight of the indicators at all levels, and evaluate six urban main roads, six urban secondary main roads and six sidewalks beside access roads, which were selected randomly. Visually impaired people were then asked to evaluate the TGSIs in the pedestrian spaces along these roads. Statistical analysis and evaluation showed that the indicators used in the evaluation system were satisfactory. The evaluation results revealed problems with the standardization, safety, accessibility, continuity, comfort and aesthetics of TGSIs in the urban roadside pedestrian space of Gulou. Analysis of the combined data showed that travel conditions for the visually impaired are currently worse in the old city area than in the new city area and that they are worse in low-grade pedestrian space than along high-grade roads. In order to solve these problems, strategies are put forward for improving the quality of TGSIs in the pedestrian space of Nanjing’s Gulou District in four aspects: improving TGSI structure, optimizing TGSI location, improving the TGSI system, and adapting TGSI implementation according to local conditions
Study on bonding compression-shear performance between industrial green fiber-reinforced concrete and old concrete
Get PDFIndustrial green fiber-reinforced concrete, a new hybrid high performance environmental protection material, can be made by adding recycled steel fibers into concrete in a certain proportion. As a composite material used in the construction industry, it can provide a new research direction for national green and sustainable development. This paper studied the interface bonding mechanism of normal steel fiber-reinforced old and new concrete and industrial green fiber-reinforced concrete and old concrete by using a self-made new fixture, and discussed the influence of compressive stress, types of steel fibers and recycled steel fiber content on the bonding compression-shear performance of specimens. The results show that the bonding compression-shear performance of specimens gradually increases with the increases of the compressive stress acting perpendicular to the shearing surface within the range of low compressive stress, and when the compressive stress is from 0.2 MPa to 1.0 MPa, the increased amplitude of the bonding compression-shear performance of specimens gradually increases, when the compressive stress is from 0.6 MPa to 1.0 MPa, the increased amplitude of the bonding compression-shear performance of specimens reaches the maximum, and when the compressive stress is from 1.0 MPa to 1.4 MPa, the increased amplitude of the bonding compression-shear performance of specimens decreases. Under the same conditions, the effect of the recycled steel fibers on improving the bonding compression-shear performance between old and new concrete is better than normal steel fibers. The bonding compression-shear performance between old and new concrete gradually increases with the increases of the volume ratio of recycled steel fibers, and when the fiber content is from 0.0 % to 1.0 %, the increased amplitude of the bonding compression-shear performance of specimens gradually increases, when the fiber content is from 0.5 % to 1.0 %, the increased amplitude of the bonding compression-shear performance of specimens reaches the maximum, and when the fiber content is from 1.0 % to 1.5 %, the increased amplitude of bonding compression-shear performance of specimens decreases. The simulation results of industrial green fiber-reinforced concrete and old concrete specimens with fiber content of 1.5 % under different compressive stresses are basically in agreement with the experimental results. This study can provide references for the research of bonding compression-shear behavior of steel fiber-reinforced old and new concrete materials and the recycling of steel wire from waste tires. Industrial green fiber-reinforced concrete, a new hybrid high performance environmental protection material, can be made by adding recycled steel fibers into concrete in a certain proportion. As a composite material used in the construction industry, it can provide a new research direction for national green and sustainable development. This paper studied the interface bonding mechanism of normal steel fiber-reinforced old and new concrete and industrial green fiber-reinforced concrete and old concrete by using a self-made new fixture, and discussed the influence of compressive stress, types of steel fibers and recycled steel fiber content on the bonding compression-shear performance of specimens. The results show that the bonding compression-shear performance of specimens gradually increases with the increases of the compressive stress acting perpendicular to the shearing surface within the range of low compressive stress, and when the compressive stress is from 0.2 MPa to 1.0 MPa, the increased amplitude of the bonding compression-shear performance of specimens gradually increases, when the compressive stress is from 0.6 MPa to 1.0 MPa, the increased amplitude of the bonding compression-shear performance of specimens reaches the maximum, and when the compressive stress is from 1.0 MPa to 1.4 MPa, the increased amplitude of the bonding compression-shear performance of specimens decreases. Under the same conditions, the effect of the recycled steel fibers on improving the bonding compression-shear performance between old and new concrete is better than normal steel fibers. The bonding compression-shear performance between old and new concrete gradually increases with the increases of the volume ratio of recycled steel fibers, and when the fiber content is from 0.0 % to 1.0 %, the increased amplitude of the bonding compression-shear performance of specimens gradually increases, when the fiber content is from 0.5 % to 1.0 %, the increased amplitude of the bonding compression-shear performance of specimens reaches the maximum, and when the fiber content is from 1.0 % to 1.5 %, the increased amplitude of bonding compression-shear performance of specimens decreases. The simulation results of industrial green fiber-reinforced concrete and old concrete specimens with fiber content of 1.5 % under different compressive stresses are basically in agreement with the experimental results. This study can provide references for the research of bonding compression-shear behavior of steel fiber-reinforced old and new concrete materials and the recycling of steel wire from waste tires
Estudio desarrolló un análisis global sobre los impactos del riego agrícola en la ocurrencia de deslizamientos en masa
Get PDFLos deslizamientos en masa son un fenómeno natural. Sin embargo, estos también pueden ser gatillados por actividades humanas, como construcción de caminos, deforestación, etc. Esta nota se basa en los resultados de un análisis global (literatura publicada en español, inglés y chino) sobre un inusual tipo de deslizamiento antrópico: los gatillados por el riego agrícola. Este análisis de cooperación internacional concluye que los deslizamientos producidos por el riego agrícola se han incrementado exponencialmente en las últimas décadas, siendo más comunes en climas secos con lluvias concentradas en los meses de verano. Similarmento, este tipo de deslizamientos ocurre en cierto tipo de materiales geológicos, y la mayoría de los 82 casos documentados a nivel mundial se han producido en Asia y América del Sur.Los deslizamientos en masa son un fenómeno natural. Sin embargo, estos también pueden ser gatillados por actividades humanas, como construcción de caminos, deforestación, etc. Esta nota se basa en los resultados de un análisis global (literatura publicada en español, inglés y chino) sobre un inusual tipo de deslizamiento antrópico: los gatillados por el riego agrícola. Este análisis de cooperación internacional concluye que los deslizamientos producidos por el riego agrícola se han incrementado exponencialmente en las últimas décadas, siendo más comunes en climas secos con lluvias concentradas en los meses de verano. Similarmento, este tipo de deslizamientos ocurre en cierto tipo de materiales geológicos, y la mayoría de los 82 casos documentados a nivel mundial se han producido en Asia y América del Sur
Comportamiento en la absorción de Na y Pb en plantas de cucurbitáceas e inoculación de micorrizas arbusculares nativas en especie tolerante y suceptible
No full textNa and Pb in high concentrations can affect the growth of crops. An alternative to mitigate plant stress caused by these elements is inoculation with arbuscular mycorrhizal fungi. The present work was carried out with the objective of evaluating Na and Pb uptake in Cucurbitaceae plants (Citrullus lanatus, Cucumis melo, Cucurbita ecuadoriensis, Cucurbita moschata) under controlled conditions, in addition to evaluating the effect of a consortium of arbuscular mycorrhizal fungi on a tolerant and a susceptible species. The experiments were conducted in rice husk:sand substrate in a 1:1 ratio. Na and Pb were applied at concentrations of 0, 97, 309, 529, 741 mg/kg and 0, 150, 250, 500, 1000 mg/kg, respectively. Agronomic parameters were evaluated and the accumulation of both elements in the biomass was quantified by atomic absorption spectrometry. As a result, Cucurbita ecuadoriensis, a Na and Pb tolerant species, accumulated 10 301.3 mg/kg Na and 5293.1 mg/kg Pb in its total biomass. Meanwhile, the susceptible species Cucumis melo accumulated 22 091.6 mg/kg Na and 14 407 mg/kg Pb in its total biomass. In the trial with inoculation of arbuscular mycorrhizal fungi, a decrease was observed in Cucurbita ecuadoriensis, which reached 3419.3 mg/kg Na and 4866.1 mg/kg Pb. Likewise, Cucumis melo accumulated 8681 mg/kg Na and 3133.1 mg/kg Pb in its total biomass. In conclusion, inoculation with AMF allowed both plants to accumulate less Na and Pb in their systems.El Na y el Pb en concentraciones altas pueden afectar el desarrollo de los cultivos. Una alternativa para mitigar el estrés vegetal ocasionado por estos elementos es la inoculación con hongos micorrízicos arbusculares (HMA). El presente trabajo se realizó con el objetivo de evaluar la absorción del Na y Pb en plantas de cucurbitáceas (Citrullus lanatus, Cucumis melo, Cucurbita ecuadoriensis, Cucurbita moschata) bajo condiciones controladas, además de evaluar el efecto de un consorcio de hongos micorrízicos arbusculares sobre una especie tolerante y otra susceptible. Los experimentos se realizaron en sustrato (cascarilla de arroz:arena en proporción 1:1). El Na y el Pb fueron aplicados a concentraciones de 0, 97, 309, 529, 741 mg/kg y 0, 150, 250, 500, 1000 mg/kg, respectivamente. Se evaluaron parámetros agronómicos y se cuantificó la acumulación de ambos elementos en la biomasa por espectrometría de absorción atómica. Como resultado, Cucurbita ecuadoriensis, especie tolerante a Na y Pb, acumuló en su biomasa total 10 301.3 mg/kg de Na y 5293.1 mg/kg de Pb. Mientras, la especie susceptible Cucumis melo acumuló 22 091.6 mg/kg de Na y 14 407 mg/kg de Pb en su biomasa total. En el ensayo con inoculación de hongos micorrízicos arbusculares se observó una disminución en Cucurbita ecuadoriensis que alcanzó 3419.3 mg/kg de Na y 4866.1 mg/kg de Pb. Asimismo, Cucumis melo acumuló 8681 mg/kg de Na y 3133.1 mg/kg de Pb en su biomasa total. En conclusión, la inoculación con HMA, permitió que ambas plantas acumulen menor cantidad de Na y Pb en sus sistemas
Cálculos estequiométricos de factores de emisión para estimar emisiones fugitivas de gases de efecto invernadero en un centro de acopio de residuos sólidos
Get PDFEmission Factors (EF) are representative values which relate the amount of gases released into the atmosphere by the development of an activity, allowing the estimation of emission rates (e.g., in the solid waste generated). The organic fraction of municipal solid waste (OFMSW) requires particular EF. In this study, emissions of carbon dioxide equivalent (CO2e) in a higher education institution (HEI) were estimated. The EFs from OFMSW were obtained based on stoichiometry calculations considering the aerobic and anaerobic decomposition processes. The monitoring of municipal solid waste (MSW) daily generation during 2017 in the HEI and the use of bibliographic EF allowed the calculation of the initial emission rate. The HEI studied has 26 sources of waste generation. It generated 31.05 t/yr of MSW, an average of 146.5 kg/d and a per capita generation of 0.07 kg/d. Eighteen by-products were identified, 13 of them recoverable. Initially, the negative emission was 7617.4 kg CO2e, attributable to 7.08 t of recoverable MSW, and the positive emission was 1178.1 kg CO2e from final disposal. The EFs obtained adjusted the negative final emission to 8153 t CO2e and the positive final emission to 651.3 kg CO2e. Proper management of the MSW generated in work or educational centers allows reducing environmental impacts, recovering raw materials and energy.Los factores de emisión (FE) son valores representativos que relacionan la cantidad de gases liberados a la atmósfera por el desarrollo de una actividad y permiten la estimación de tasas de emisión, por ejemplo en los residuos sólidos generados. La fracción orgánica de los residuos sólidos urbanos (FORSU) requiere FE particulares. En este estudio se estimaron las emisiones de dióxido de carbono equivalente (CO2e) en una institución de educación superior (IES). Los FE de la FORSU fueron obtenidos mediante cálculos estequiométricos considerando los procesos de descomposición aerobia y anaerobia. El monitoreo de la generación diaria de residuos sólidos urbanos (RSU) en 2017 en la IES y el uso de FE bibliográficos permitió el cálculo de la tasa de emisión inicial. La IES estudiada cuenta con 26 fuentes de generación de residuos que generaron 31.05 t/año de RSU, un promedio de 146.5 kg/d y una generación per cápita de 0.07 kg/d. Se identificaron 18 subproductos, de los cuales 13 son valorizables. Inicialmente, la emisión negativa fue de 7617.4 kg CO2e, atribuibles a 7.08 t de RSU valorizables, y la emisión positiva fue de 1178.1 kg CO2e por la disposición final. Los FE obtenidos ajustaron la emisión final negativa a 8153 t CO2e y la emisión final positiva a 651.3 kg CO2e. El manejo adecuado de los RSU generados en centros de trabajo o educativos permite disminuir los impactos ambientales, recuperando materias primas y energía
Impactos ambientales de una biorrefinería HMZS-NN
No full textThe life cycle analysis (LCA) of a six-stage biorefinery (BRF) called HMEZS-NN (hydrogen, methane, acids, solvents, enzymes, saccharified and nanobioparticles), which processes the organic fraction of municipal solid waste to obtain bioenergy and value-added products (concentrated organic acids and solvents, cellulolytic and xylanolytic enzymes, and nanobioparticles) for the water remediation industry, was carried out. The 18 intermediate point impact categories were analyzed with the 2016 hierarchical ReCiPe method. It was found that the BRF is self-sufficient in total energy, in an amount close to 600 MJ that consists entirely of high and low voltage electrical energy,but it has a 37 % deficit in the heat category. With an ad hoc sensitivity analysis, it was found that by raising the value of the fraction of fermented solids generated by the bioreactor H destined for the methanogenic bioreactor M from 40 to 54.12 %, it could be self-sufficient in heat and generate a very significant surplus of electrical energy. The stages that contributed significantly to several midpoint impact categories were the Z and NN stages and various processes nested within them. Less frequently, and acting on specific categories, stages M (in global warming, for example), H, and E (extraction of organic acids, essential in stratospheric ozone deterioration) were placed. In the various categories of ecotoxicity, a marked trend was noted for Z and NN predominant contribution. Almost all processes related to the purification of residues from the production of phosphoric acid and various processes for treating mining waste, coal, ash, and tailings are non-explicit.Se realizó el análisis de ciclo de vida (ACV) de una biorrefinería (BRF) de seis etapas tipo HMEZS-NN (hidrógeno, metano, ácidos, solventes, enzimas, sacarificados y nanobiopartículas), la cual procesa la fracción orgánica de residuos sólidos urbanos para obtener bioenergías y productos de valor agregado (concentrado de ácidos orgánicos y solventes, enzimas celulolíticas y xilanolíticas, y nanobiopartículas) para la industria de remediación de aguas. Se analizaron las 18 categorías de impacto de punto intermedio con el método ReCiPe jerárquico 2016. Se encontró que la BRF es autosuficiente en energía total, en una cantidad cercana a los 600 MJ, que consiste totalmente en energía eléctrica de alto y bajo voltaje, pero deficitaria en un 37 % en el rubro calor. Con un análisis de sensibilidad ad hoc, se encontró que subiendo el valor de la fracción de sólidos fermentados que genera el biorreactor H y que se destina al biorreactor metanogénico M del 40 al 54.12 %, la BFR podría ser autosuficiente en calor y además generar un execedente muy significativo de energía eléctrica. Las etapas que contribuyeron significativamente a varias de las categorías de impacto de punto intermedio fueron las etapas de producción de enzimas (Z) y nanopartículas (NN), y de varios procesos anidados en ellas. Con menor frecuencia, y actuando sobre categorías particulares, se colocaron la etapa M de metanogénesis (en calentamiento global, por ejemplo), hidogénesis y E (extracción de ácidos orgánicos), importante para el deterioro de ozono estratosférico, por ejemplo. En las diversas categorías de ecotoxicidad se notó tendencia marcada a la contribución predominante de Z y NN, y de los procesos relacionados con purificación de residuos de la producción de ácido fosfórico y varios procesos de tratamiento de residuales de minería, de carbón, cenizas y jales. La mayoría de esos procesos no son explícitos en la base de datos del Software
Analysis of the practices and technologies used for the treatment of brominated plastics of WEEE in Guadalajara city, Mexico
Get PDFThe increase in waste electrical and electronic equipment (WEEE) has become an attractive waste for the recycling industry, mainly due to the high volume found in the waste flow that can be transformed into other products. The purpose of this study is to investigate the treatments applied to WEEE brominated plastics in companies of recycling in the Metropolitan Area of Guadalajara (MAG), Mexico, and the comparison with international guidelines. The information-gathering was obtained through interviews and visits; fourteen companies dedicated to the field of recovery, treatment and/or recycling of electronic waste were identified. Only seven companies allowed the study to be carried out, and only five companies provided plastics samples. Eighty-six samples of different kinds of plastics were obtained and analyzed using the Handheld X-ray fluorescence (HXRF) technique, and the atypical cases have undergone an analysis of X-ray photoelectron spectroscopy (XPS) and X-ray energy dispersive spectrometer (EDS). Bromine was the predominant element in the samples analyzed, which sometimes exceeded the permissible limits of the European Directive 4 to 10 times, meaning that the concentration ranges go from 10000 to 39500 mg/kg. It was identified bromine as a chemical precursor of flame retardants, which is prohibited by international agreements because they cause damage to the environment and public health. As a result, the companies dedicated to the treatment and/or recycling of plastics from WEEE do not follow the practices and technologies used internationally. However, considering the circular economy, this is relevant to establish limits of traces of contaminants in recycled plastics.The increase in waste electrical and electronic equipment (WEEE) has become an attractive waste for the recycling industry, mainly due to the high volume found in the waste flow that can be transformed into other products. The purpose of this study is to investigate the treatments applied to WEEE brominated plastics in companies of recycling in the Metropolitan Area of Guadalajara (MAG), Mexico, and the comparison with international guidelines. The information-gathering was obtained through interviews and visits; fourteen companies dedicated to the field of recovery, treatment and/or recycling of electronic waste were identified. Only seven companies allowed the study to be carried out, and only five companies provided plastics samples. Eighty-six samples of different kinds of plastics were obtained and analyzed using the Handheld X-ray fluorescence (HXRF) technique, and the atypical cases have undergone an analysis of X-ray photoelectron spectroscopy (XPS) and X-ray energy dispersive spectrometer (EDS). Bromine was the predominant element in the samples analyzed, which sometimes exceeded the permissible limits of the European Directive 4 to 10 times, meaning that the concentration ranges go from 10000 to 39500 mg/kg. It was identified bromine as a chemical precursor of flame retardants, which is prohibited by international agreements because they cause damage to the environment and public health. As a result, the companies dedicated to the treatment and/or recycling of plastics from WEEE do not follow the practices and technologies used internationally. However, considering the circular economy, this is relevant to establish limits of traces of contaminants in recycled plastics
Photo-fermentative hydrogen production from organic acids mixtures evaluated through predictive models for Rhodobacter capsulatus strains
Get PDFThis research aimed to evaluate growth and hydrogen production from Rhodobacter capsulatus DSM155 and B10 strains in function of volatile fatty acids (VFA) media composition, as well as to assess the light intensity effect on hydrogen production. The growth of DSM155 and B10 was verified in media containing either acetic acid, butyric acid, or sodium lactate, or a mixture of them (ABL medium), being the ABL medium that produced the maximum cell dry weight, 2.15 and 1.67 g/L for DSM155 and B10, respectively. Biohydrogen production was evaluated in media containing acetic and butyric acids (AB medium), and ABL medium. Both strains presented the highest hydrogen production using ABL medium, being the highest 239.2 mL H2 for DSM155. Finally, light intensity (10, 20, and 30 klux) effect on biohydrogen production was studied using the best strain and medium, i.e., DSM155 and ABL medium. DSM155 produced hydrogen increasingly in the order 10, 20, and 30 klx (2753.5, 2850.5, and 2946.3 mL H2/Lop, respectively); however, the light conversion efficiency into hydrogen showed an inverse trend, 7.47, 4.16, and 2.67 %. In conclusion, R. capsulatus DSM155 is advisable for biohydrogen production using ABL medium in the range 10-30 klux. Moreover, further work is recommended on DSM 155 using organic acid-rich real effluents from dark fermentation.This research aimed to evaluate growth and hydrogen production from Rhodobacter capsulatus DSM155 and B10 strains in function of volatile fatty acids (VFA) media composition, as well as to assess the light intensity effect on hydrogen production. The growth of DSM155 and B10 was verified in media containing either acetic acid, butyric acid, or sodium lactate, or a mixture of them (ABL medium), being the ABL medium that produced the maximum cell dry weight, 2.15 and 1.67 g/L for DSM155 and B10, respectively. Biohydrogen production was evaluated in media containing acetic and butyric acids (AB medium), and ABL medium. Both strains presented the highest hydrogen production using ABL medium, being the highest 239.2 mL H2 for DSM155. Finally, light intensity (10, 20, and 30 klux) effect on biohydrogen production was studied using the best strain and medium, i.e., DSM155 and ABL medium. DSM155 produced hydrogen increasingly in the order 10, 20, and 30 klx (2753.5, 2850.5, and 2946.3 mL H2/Lop, respectively); however, the light conversion efficiency into hydrogen showed an inverse trend, 7.47, 4.16, and 2.67 %. In conclusion, R. capsulatus DSM155 is advisable for biohydrogen production using ABL medium in the range 10-30 klux. Moreover, further work is recommended on DSM 155 using organic acid-rich real effluents from dark fermentation
Steel fibers from waste tires as reinforcements in concrete: Analysis of bond mechanism
Get PDFThrough the prior art, steel fibers can be extracted from waste tires after recycling, hereinafter referred to as recycled steel fibers. This paper mainly studies the bond performance between a single recycled steel fiber and concrete, to attain the overall bond strength of recycled steel fibers reinforced concrete. By measuring the load displacement curve of the recycled steel fibers under pullout, we ascertain the maximum bonding stresses of the recycled steel fibers with different depths, angles and shapes while undergoing interfacial pull-out. At the same time, through observations and calculations, the failure phenomena of three stages and the changing trend of bond stresses of recycled steel fibers along the anchorage section are obtained. It is evidenced that the recycled steel fibers reinforced concrete has good interfacial bonding performance. Numerical simulation results of fiber pull-out process via the finite elements provide conditions for the analysis of bond strength of recycled steel fibers reinforced concrete cubes under different circumstances.Through the prior art, steel fibers can be extracted from waste tires after recycling, hereinafter referred to as recycled steel fibers. This paper mainly studies the bond performance between a single recycled steel fiber and concrete, to attain the overall bond strength of recycled steel fibers reinforced concrete. By measuring the load displacement curve of the recycled steel fibers under pullout, we ascertain the maximum bonding stresses of the recycled steel fibers with different depths, angles and shapes while undergoing interfacial pull-out. At the same time, through observations and calculations, the failure phenomena of three stages and the changing trend of bond stresses of recycled steel fibers along the anchorage section are obtained. It is evidenced that the recycled steel fibers reinforced concrete has good interfacial bonding performance. Numerical simulation results of fiber pull-out process via the finite elements provide conditions for the analysis of bond strength of recycled steel fibers reinforced concrete cubes under different circumstances