Revista Internacional de Contaminación Ambiental
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INTRODUCTION
Get PDFENVIRONMENT, DEVELOPMENT AND SUSTAINABILITYENVIRONMENT, DEVELOPMENT & SUSTAINABILIT
DESARROLLO DE UN MODELO MATEMÁTICO PARA EL BIOSECADO DE RESIDUOS SÓLIDOS ORGÁNICOS EN PILAS
Get PDFA deterministic mathematical model was developed for biodrying a pile of organic solid waste inside a structure of glasshouse. The model included mass transfer, heat transfer, microbial growth and degradation of organic matter. The mathematical formulation is integrated by a system of four differential equations, obtained from a balance of mass and heat in the center of the pile, which are used to calculate: (1) water evaporation, (2) microbial growth, 3) consumption of organic matter, and 4) temperature. The first equation determined the moisture loss through the mass transfer coefficient and the air humidity gradient; the second one used the logistic model of microbial growth; the third one used the organic matter consumption model, and the fourth equation considered the heats of microbial metabolism, natural convection cooling-heating and the enthalpy for evaporation. The model is a useful tool for predicting microbial activity times and drying, as well as the degree of degradation of organic matter. In the particular case of this study, the model shows that the microbial activity only degraded 13 % of the organic matter, had a period of duration of 30 days during which 73% of the humidity of the pile was lost; raised the temperature of the pile to 65º C, and increased five times the rate of evaporation, but only contributed 13% of the heat for evaporation and the rest was contributed by solar radiation. Se desarrolló un modelo matemático determinístico para representar el proceso de biosecado de una pila de residuos sólidos orgánicos dentro de una estructura tipo invernadero. El modelo incluye transferencia de masa, transferencia de calor, crecimiento microbiano y degradación de la materia orgánica. La formulación matemática está integrada por un sistema de cuatro ecuaciones diferenciales, obtenidas mediante balances de masa y energía en el centro de la pila, para calcular: 1) evaporación de agua, 2) crecimiento microbiano, 3) consumo de materia orgánica y 4) temperatura. La primera determinó la pérdida de humedad a través del coeficiente de transferencia de masa; la segunda empleó el modelo logístico de crecimiento microbiano; la tercera utilizó el modelo de consumo de materia orgánica, y la cuarta integró el modelo de generación de calor microbiano, el modelo de enfriamiento-calentamiento por convección natural y la entalpía para evaporación. El modelo es una herramienta útil para predecir los tiempos de actividad microbiana y secado de la pila, así como el grado de degradación de la materia orgánica durante el biosecado. Para el caso particular del presente trabajo, el modelo nos permitió mostrar que la actividad microbiana sólo degrada el 13 % de la materia orgánica; que tiene un periodo de duración de 30 días durante los cuales se perdió el 63 % de la humedad de la pila; que elevó a 65ºC la temperatura de la pila, y que incrementó cinco veces la velocidad de evaporación, aunque el calor metabólico sólo aportó el 13 % del calor para la evaporación y el resto fue aportado por la radiación solar
EVALUATION OF LEAD TOLERANT PLANT GROWTH PROMOTING RHIZOBACTERIA FOR PLANT GROWTH AND PHYTOREMEDIATION IN LEAD CONTAMINATION
Get PDFThe present study was conducted to evaluate five pre-characterized lead tolerant plant growth promoting rhizobacteria: Pseudomonas gessardii strain BLP141 (S2), Pseudomonas fluorescens A50 (S5), Pseudomonas syringae pv. syringae B728a (S6), Pseudomonas stutzeri strain 28a24 (S8) and Pseudomonas fluorescens strain LMG 2189 (S10), for their plant growth promotion, phytoremediation potential and physiological response on Helianthus annuus L. as test crop, exposed to different lead concentrations (300, 600 and 900 mg/kg). Crop was harvested after 30 days of sowing and data regarding growth parameters (root shoot length, root shoot fresh and dry weights), physiological attributes (photosynthetic rate, transpiration rate and substomatal CO2), and lead content in root and shoot of sunflower, were recorded. Results revealed that lead contamination decreased the growth and physiological attributes of plants at all levels of lead stress; however inoculation with lead tolerant rhizobacteria reversed the toxic effect of lead on the plants and improved the growth and physiological attributes of sunflower in lead contamination, as compared to plants grown in the un-inoculated lead contaminated treatments. Among the five isolates, S2, S5 and S10 promoted more growth, improving the physiological attributes and phytoremediation potential of plants at all levels of contamination as compared to plants grown in lead stress without inoculation.The present study was conducted to evaluate five pre-characterized lead tolerant plant growth promoting rhizobacteria: Pseudomonas gessardii strain BLP141 (S2), Pseudomonas fluorescens A50 (S5), Pseudomonas syringae pv. syringae B728a (S6), Pseudomonas stutzeri strain 28a24 (S8) and Pseudomonas fluorescens strain LMG 2189 (S10), for their plant growth promotion, phytoremediation potential and physiological response on Helianthus annuus L. as test crop, exposed to different lead concentrations (300, 600 and 900 mg/kg). Crop was harvested after 30 days of sowing and data regarding growth parameters (root shoot length, root shoot fresh and dry weights), physiological attributes (photosynthetic rate, transpiration rate and substomatal CO2), and lead content in root and shoot of sunflower, were recorded. Results revealed that lead contamination decreased the growth and physiological attributes of plants at all levels of lead stress; however inoculation with lead tolerant rhizobacteria reversed the toxic effect of lead on the plants and improved the growth and physiological attributes of sunflower in lead contamination, as compared to plants grown in the un-inoculated lead contaminated treatments. Among the five isolates, S2, S5 and S10 promoted more growth, improving the physiological attributes and phytoremediation potential of plants at all levels of contamination as compared to plants grown in lead stress without inoculation
EFFECTS OF NOISE EMITTED BY MILITARY AIRCRAFT ON HOUSING CLOSE TO AN AIR BASE: THE CASE OF GANDO AIR BASE (SPAIN)
Get PDFAssessing the impact of environmental externalities has become one of the essential aspects in making economic and urban planning decisions. Our goal focuses on the innovative assessment of noise pollution emitted by military aircraft located at Gando Air Base in 2012. Its impact on the housing market was analyzed for 6447 households affected by more than 55 decibels, limiting our study to three municipalities of Gran Canaria (Spain): Telde, Agüimes and Ingenio. We propose to test several specifications for the hedonic price model and we test among them. This is a basic pre-requisite to estimate the parameters needed to inform policy markets. Our preferred model is a semi-logarithmic specification. We conclude from its results that noise pollution emitted by military aircraft positively affects the price of housings in the area when they are between 55 and 70 decibels so the fact that a property is near a noise source is not in itself conclusive evidence of a loss of real state values.Assessing the impact of environmental externalities has become one of the essential aspects in making economic and urban planning decisions. Our goal focuses on the innovative assessment of noise pollution emitted by military aircraft located at Gando Air Base in 2012. Its impact on the housing market was analyzed for 6447 households affected by more than 55 decibels, limiting our study to three municipalities of Gran Canaria (Spain): Telde, Agüimes and Ingenio. We propose to test several specifications for the hedonic price model and we test among them. This is a basic pre-requisite to estimate the parameters needed to inform policy markets. Our preferred model is a semi-logarithmic specification. We conclude from its results that noise pollution emitted by military aircraft positively affects the price of housings in the area when they are between 55 and 70 decibels so the fact that a property is near a noise source is not in itself conclusive evidence of a loss of real state values
DINÁMICA DE LA CONCENTRACIÓN DE COBRE, PLOMO, MERCURIO Y ARSÉNICO EN SEDIMENTOS DEL RÍO COPIAPÓ, CHILE
Get PDFThe Copiapó river basin, to the south of the Atacama desert, has a strong anthropic intervention due to mining, agricultural and urban activities. The presence of mining environmental tailings in the basin is relevant, mainly when they are close to watercourses and populated areas. In this work the relationship between the variations of copper, lead, mercury and arsenic concentrations related to the sediment transport dynamics along a year was studied. From five points along the Copiapó river, including areas of mining, agricultural and urban intervention, the sediments were analyzed for granulometry and chemical composition. The results show that the temporal variation of elements concentrations was proportionally inverse to the transport of the finest fraction of the sediment. This is related to changes in sediments transport, influenced by sporadic rains, snow melting, sediment supply from upstream sediments and wind events in areas with mining activity.La cuenca del río Copiapó, al sur del desierto de Atacama, tiene una fuerte intervención antrópica debido a la actividad minera, agrícola y urbana. La presencia de pasivos ambientales mineros en la cuenca es relevante, ya que éstos se encuentran cerca de cursos de agua y zonas pobladas. En este trabajo se estudió la relación entre la variación de concentraciones de cobre, plomo, mercurio y arsénico con la dinámica de trasporte de sedimentos a lo largo de un año. Se analizó la granulometría y composición química de los sedimentos presentes en cinco puntos del río Copiapó, incluyendo zonas de intervención minera, agrícola y urbana. Los resultados muestran que la variación temporal de la concentración de los elementos analizados es inversamente proporcional al incremento de la transferencia de la fracción más fina de sedimento. Lo anterior se relaciona con cambios en el transporte de sedimentos, el cual está influido por lluvias esporádicas, deshielo, aporte de sedimentos desde aguas arriba y eventos eólicos en las zonas con actividad minera
RIESGO ECOLÓGICO POTENCIAL POR ARSÉNICO EN LA DESEMBOCADURA DEL RÍO LOA, NORTE DE CHILE
Get PDFPotential ecological risk by arsenic in the available fractions of the sediment in the river, lagoon, mixing zone and beaches bordering the mouth of the Loa River, north of Chile, was determined based on low and medium range effects. The distribution constant, geoaccumulation index and As enrichment factor were deduced. To estimate reactive As, three simple extraction procedures were compared. In order to obtain the risk assessment code, the first two stages of sequential Tessier extraction and bioavailability were applied according to the modified BCR schema. The salty and alkaline continental waters showed a reducing character, low OD, N/P and Cu, but high As (1.13-1.80 mg/l), diluted in the sea at 0.012 mg/L. The neutral continental sediments presented low organic matter (2-6%), acceptable levels of N/P, CaCO3 (5.3-31%) and Cu, but elevated As (516-856 mg/kg). As reached levels of 20 mg/kg in marine sediments. According to the geoaccumulation index values, there was terrestrial but not marine pollution, although the enrichment factors confirm the presence of high potential risk at the river mouth. Simple extractions and the risk assessment code point to As as mobile and bioavailable. The level of As in the fluvial sediment associated with interchangeable, reducible and oxidizable fractions confirm potential risk for the ecosystem under alkaline and reducing conditions. On the other hand, in the coastal border As was found associated mainly with residual and interchangeable fractions, which reduces this potential risk.En el río, laguna y zona de mezcla del río Loa (norte de Chile), así como en las playas aledañas a su desembocadura, se determinó el riesgo ecológico potencial por arsénico en las fracciones disponibles del sedimento, con base en los efectos de rango bajo y medio. Se dedujeron la constante de distribución, el índice de geoacumulación (Igeo) y el factor de enriquecimiento (FE) de As. Para estimar el As reactivo se compararon tres procedimientos de extracción simple, y con el fin de obtener el código de evaluación de riesgo se aplicaron las dos primeras etapas de la extracción secuencial de Tessier y la biodisponibilidad según el esquema BCR modificado. Las aguas continentales saladas y alcalinas presentaron un carácter reductor, bajos contenidos de OD, N/P y Cu, pero As elevado (1.13-1.80 mg/L), diluido en el mar a 0.012 mg/L. Los sedimentos continentales neutros presentaron materia orgánica baja (2-6 %), niveles aceptables de N/P, CaCO3 (5.3-31 %) y Cu, pero As elevado (516-856 mg/kg). En sedimentos marinos alcanzó 20 mg/kg de As. Los valores del Igeo establecen la categoría de contaminación terrestre, pero no marina, aunque los FE confirman la presencia de riesgo potencial elevado en la desembocadura. Las extracciones simples y el código de evaluación de riesgo lo señalan como móvil y biodisponible. El nivel de As en el sedimento fluvial asociado a las fracciones intercambiable, reducible y oxidable, confirman riesgo potencial para el ecosistema en condiciones alcalinas y reductoras. En cambio, en el borde costero, el As se encuentra asociado mayoritariamente a las fracciones residual e intercambiable, lo cual reduce el riesgo potencial
POTENCIAL DE RESIDUOS INDUSTRIALES GENERADOS EN CIUDAD JUÁREZ, CHIHUAHUA, MÉXICO, COMO COMBUSTIBLES ALTERNOS EN UN HORNO CEMENTERO
Get PDFIn Ciudad Juárez, Chihuahua, high amounts of non-hazardous solid wastes are produced mainly by the manufacturing, nut processing and wood industries. Low-cost and environmental friendly alternatives are necessary to properly manage this kind of wastes. Recyclability is not feasible due to the predominance of waste mixtures and composite residual materials. Energetic valorization of these wastes as alternative fuels is considered as a disposal alternative with both environmental and economic advantages. The objective of this study was to assess the potential of solid non-recyclable wastes produced in Ciudad Juárez, Chihuahua as alternative fuels in a kiln. First, the different categories of wastes were classified and then physically and chemically characterized based on standard methods. Biomass wastes (sawdust and nut shell) were the highest fraction regarding weight percent, followed by the wastes categorized as energetically efficient residual organic fraction (EEROF), which includes mixtures involving wood, carton, plastics and automotive fabrics. The lower heating values, from low to high (8869, 5895 and 3553 kcal/kg), corresponded to tires, EEROF and biomass wastes, respectively. The chlorine content among EEROF wastes, polyurethane plastic and some automotive fabrics was higher than the established limits for the cement industry, thus they were discarded. The final EEROF wastes formulation, supplemented with biomass wastes and tires, complies with the recommended values for critical parameters to be employed as alternative fuels, so these non-recyclable waste streams could be energetically valorized.En Ciudad Juárez, Chihuahua, México, se generan cantidades considerables de residuos sólidos no peligrosos, producidos principalmente por las industrias de manufactura, nogalera y maderera. El manejo integral de estos residuos requiere alternativas de tratamiento con mínimos impactos ambientales y económicos. Debido a que una fracción importante se compone de mezclas y materiales compuestos, el reciclaje no es viable. El aprovechamiento de la energía de estos residuos como combustibles alternos se considera una alternativa para su desecho. El propósito del estudio fue evaluar el potencial de los residuos sólidos industriales no reciclables generados en Ciudad Juárez, Chihuahua, como combustibles alternos para un horno cementero. En primer término, se clasificaron las diferentes corrientes de residuos y luego se caracterizaron física y químicamente de acuerdo con métodos estandarizados. Los residuos de biomasa comprendieron una fracción mayor como porcentaje de masa, seguidos por los categorizados como fracción residual orgánica de eficiencia energética (FROEE), que agrupan mezclas residuales de madera, papel y cartón, plásticos, y vestiduras automotrices. El poder calorífico inferior, ordenado de mayor a menor (8869, 5895 y 3553 kcal/kg), correspondió a los residuos de neumáticos, FROEE y biomasa, respectivamente. De los residuos FROEE, se identificó que el porcentaje en masa de cloro en poliuretano y algunas vestiduras automotrices era superior al límite establecido por los criterios internacionales de la industria cementera, por lo que se descartaron. La mezcla final de residuos FROEE, complementada con residuos de biomasa y de neumáticos, cumple con los parámetros críticos recomendados para uso como combustibles alternos; por tanto, las corrientes de residuos no reciclables pueden ser valorizadas energéticamente
DEGRADACIÓN DE LA MEZCLA COMERCIAL DE LOS HERBICIDAS ATRAZINA Y AMETRINA, UTILIZANDO CULTIVOS CON CÉLULAS EN SUSPENSIÓN E INMOVILIZADAS
Get PDFThe excessive use of herbicides has caused weeds resistance to these compounds; thus, it has been implemented the use of mixtures of herbicides to ensure its effect on weeds. One of the commercial mixtures used in Mexico is that of atrazine and ametryn. Information on processes for ametryn degradation is scarce, and virtually no references to the biodegradation of the commercial mixture of atrazine and ametryn exist. In this study, the biodegradation of this commercial mixture using a microbial community in different types of cultures, and using a chemostat and biobarrier is presented. To assess the degradation capability of the microbial community, planktonic cells were used in a semi-continuous batch system. From this system, the continuous process was started. In repeated batch cultures, complete removal of both herbicides was obtained. In the continuous system, at all tested volumetric loads, the removal efficiencies of ametryn and atrazine were of 100 and 97 % respectively. During continuous operation, biofilm formation on the reactor walls was observed; thus, it was decided to install a biobarrier using volcanic rock fragments (tezontle) as biofilm support. In this system, the removal efficiencies (ŋ) and the volumetric removal rates (Rv) of the herbicide mixture were 100 % and 287 mg/L/d, respectively. At all the loading rates tested, cyanuric acid accumulation was observed; however, when the biobarrier was operated at low volumetric loading rates, considerable metabolic degradation of this intermediate was achieved.El empleo desmedido de los herbicidas ha ocasionado que las malezas generen resistencia a estos agroquímicos, por lo que se ha implementado el uso de mezclas para garantizar su efecto sobre diversos pastos indeseables. Una de las formulaciones comerciales utilizada en México es la mezcla de atrazina con ametrina. La información sobre procesos de degradación de la ametrina es escasa y prácticamente no hay referencias sobre la biodegradación de la mezcla comercial de la atrazina con ametrina. En este trabajo se presenta la biodegradación de esta mezcla comercial utilizando una comunidad microbiana en diferentes tipos de cultivo, empleando un quimiostato y una biobarrera. Para evaluar la capacidad de degradación de la comunidad microbiana se utilizaron células planctónicas en un sistema por lote semicontinuo, donde se obtuvo la remoción completa de ambos herbicidas. A partir de este sistema se inició un proceso continuo en el que, con todas las cargas volumétricas probadas, se removió el 100 % de ametrina y más del 97 % de atrazina. Durante la operación del proceso continuo se observó la formación de biopelícula en las paredes del reactor, por lo que se decidió utilizar una biobarrera con fragmentos de roca volcánica (tezontle) como soporte. En este sistema se obtuvieron eficiencias (ŋ) y velocidades volumétricas de remoción (RV) de los herbicidas, del 100 % y 287 mg/L/d, respectivamente. En todos los cultivos evaluados se observó la acumulación de ácido cianúrico; sin embargo, a bajas cargas volumétricas se alcanzó una degradación considerable de este intermediario metabólico.
COMBINED TREATMENT USING OZONE FOR CYANIDE REMOVAL FROM WASTEWATER: A COMPARISON
Get PDFCyanidation is widely used by several gold mining companies worldwide. Since its wastewaters contain cyanide, appropriate treatments must be applied to remove this pollutant. Combinations of ozone (O3), hydrogen peroxide (H2O2) and activated carbon (AC) can be used for this purpose. In this work, synthetic cyanide solutions ([CN¯]o = 15.37 mM) were treated using O3 and the combinations O3/H2O2, O3/AC and O3/H2O2/AC under alkaline conditions. O3 was produced from dry oxygen at a rate of 2.51 g O3/h([O3] gas-phase = 6.9x10–2 g/L). The concentration of cyanide (CN¯) and O3 consumption were measured and the performance of the treatments evaluated. The highest cyanide removal was reached at pH 11.0 for all cases and with 10 mg H2O2/mg O3 upon adding H2O2. In contrast, the addition of AC did not improve the cyanide removal in comparison with O3 alone. The best cyanide removal was achieved with the combination O3/H2O2 followed by the combination O3/H2O2/AC. Moreover, cyanidation effluents were treated using the combination O3/H2O2. In this case, almost a total removal of free cyanide was achieved after 3 min of treatment.Cyanidation is widely used by several gold mining companies worldwide. Since its wastewaters contain cyanide, appropriate treatments must be applied to remove this pollutant. Combinations of ozone (O3), hydrogen peroxide (H2O2) and activated carbon (AC) can be used for this purpose. In this work, synthetic cyanide solutions ([CN¯]o = 15.37 mM) were treated using O3 and the combinations O3/H2O2, O3/AC and O3/H2O2/AC under alkaline conditions. O3 was produced from dry oxygen at a rate of 2.51 g O3/h([O3] gas-phase = 6.9x10–2 g/L). The concentration of cyanide (CN¯) and O3 consumption were measured and the performance of the treatments evaluated. The highest cyanide removal was reached at pH 11.0 for all cases and with 10 mg H2O2/mg O3 upon adding H2O2. In contrast, the addition of AC did not improve the cyanide removal in comparison with O3 alone. The best cyanide removal was achieved with the combination O3/H2O2 followed by the combination O3/H2O2/AC. Moreover, cyanidation effluents were treated using the combination O3/H2O2. In this case, almost a total removal of free cyanide was achieved after 3 min of treatment
INOCULUM ADAPTATION FOR THE ANAEROBIC DIGESTION OF MEZCAL VINASSES
Get PDFVinasses are a very harmful residue of the alcohol distillation, their discharge into soil and water can cause negative environmental impacts if the appropriate treatments do not take place. Anaerobic digestion has shown to be the best technological and economical method to treat this residue, thus bioenergy can be generated as by-product of this process. Nevertheless, the slow adaptation of the microbial consortium in inoculum (activated sludge) to the substrate (mezcal vinasses) is very important to enhance the efficiency of the biogas and methane production, as well as organic matter removal. In this work, the adaptation process of the anaerobic digestion of mezcal vinasses was carried out in a 30-day period. Inoculum (activates sludge) and vinasses were mixed initially at the ratio 7:3. The feeding steps were done every seven days replacing 30 % of the total volume with new vinasses. Biogas was quantified and qualified. Biogas production reached 217 L/kgVSvinassesgenerating a daily methane content between 50 and 55 % by the end of the adaptation period. The organic matter removal efficiency was almost seven times higher at the end of the adaptation, in comparison to the beginning. This suggests that a slow adaptation process enhance the organic matter removal and eventually other pollutants in vinasses. When comparing this results with the literature, biogas and methane production were similar, nevertheless the anaerobic digestion could be optimized, in order to increase the methane content in biogas and the removal rate of organic matter.Vinasses are a very harmful residue of the alcohol distillation, their discharge into soil and water can cause negative environmental impacts if the appropriate treatments do not take place. Anaerobic digestion has shown to be the best technological and economical method to treat this residue, thus bioenergy can be generated as by-product of this process. Nevertheless, the slow adaptation of the microbial consortium in inoculum (activated sludge) to the substrate (mezcal vinasses) is very important to enhance the efficiency of the biogas and methane production, as well as organic matter removal. In this work, the adaptation process of the anaerobic digestion of mezcal vinasses was carried out in a 30-day period. Inoculum (activates sludge) and vinasses were mixed initially at the ratio 7:3. The feeding steps were done every seven days replacing 30 % of the total volume with new vinasses. Biogas was quantified and qualified. Biogas production reached 217 L/kgVSvinassesgenerating a daily methane content between 50 and 55 % by the end of the adaptation period. The organic matter removal efficiency was almost seven times higher at the end of the adaptation, in comparison to the beginning. This suggests that a slow adaptation process enhance the organic matter removal and eventually other pollutants in vinasses. When comparing this results with the literature, biogas and methane production were similar, nevertheless the anaerobic digestion could be optimized, in order to increase the methane content in biogas and the removal rate of organic matter