Navegando por Autor "Higa, L."
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Ítem Acceso Abierto Biodegradation and detoxi cation of phenolic compounds by pure and mixed indigenous cultures in aerobic reactors.(2003) Gallego, A.; Fortunato, M.; Foglia, J.; Rossi, S.; Gemini, V.; Gómez, L.; Gómez, C.; Higa, L.; Korol, S.Degradation and detoxi!cation of a mixture of persistent compounds (2-chlorophenol, phenol and m-cresol) were studied by using pure and mixed indigenous cultures in aerobic reactors. Biodegradation assays were performed in batch and continuous 9ow reactors. Biodegradation was evaluated by determining total phenols, ultraviolet spectrophotometry and chemical oxygen demand (COD). Microbial growth was measured by the plate count method. Scanning electronic microscopy was employed to observe the microbial community in the reactor. Detoxi!cation was evaluated by using Daphnia magna toxicity tests. Individual compounds were degraded by pure bacteria cultures within 27 h. The mixture of 2-clorophenol (100 mg l−1), phenol (50 mg l−1) and m-cresol (50 mg l−1) was degraded by mixed bacteria cultures under batch conditions within 36 h: 99.8% of total phenols and 92.5% of COD were removed; under continuous 9ow conditions 99.8% of total phenols and 94.9% of COD were removed. Mineralization of phenolic compounds was assessed by gas chromatography performed at the end of the batch assays and in the eAuent of the continuous-9ow reactor. Toxicity was not detected in the eAuent of the continuous-9ow reactor.? 2003 Elsevier Ltd. All rights reserved.Ítem Acceso Abierto Biodegradation and detoxi!cation of phenolic compounds by pure and mixed indigenous cultures in aerobic reactors(2001) Gallego, A.; Fortunato, M.; Foglia, J.; Rossi, S.; Gemini, V.; Gomez, L.; Gomez, C.; Higa, L.; Korol, S.Degradation and detoxi!cation of a mixture of persistent compounds (2-chlorophenol, phenol and m-cresol) were studied by using pure and mixed indigenous cultures in aerobic reactors. Biodegradation assays were performed in batch and continuous 9ow reactors. Biodegradation was evaluated by determining total phenols, ultraviolet spectrophotometry and chemical oxygen demand (COD). Microbial growth was measured by the plate count method. Scanning electronic microscopy was employed to observe the microbial community in the reactor. Detoxi!cation was evaluated by using Daphnia magna toxicity tests. Individual compounds were degraded by pure bacteria cultures within 27 h. The mixture of 2-clorophenol (100 mg l−1), phenol (50 mg l−1) and m-cresol (50 mg l−1) was degraded by mixed bacteria cultures under batch conditions within 36 h: 99.8% of total phenols and 92.5% of COD were removed; under continuous 9ow conditions 99.8% of total phenols and 94.9% of COD were removed. Mineralization of phenolic compounds was assessed by gas chromatography performed at the end of the batch assays and in the eAuent of the continuous-9ow reactor. Toxicity was not detected in the eAuent of the continuous-9ow reactor.? 2003 Elsevier Ltd. All rights reserved.Ítem Acceso Abierto Estudio y preparación de medios adsorbentes con capacidad para remover arsénico de aguas subterráneas(Congreso de Ciencias Ambientales-Consejo Profesional de Ingeniería Mecánica y Electricista (COPIME)., 2011-10) Fuse, V. ; Rodríguez Salemi, V. ; Marquina, L. ; Hildt, C. ; Juliarena, M. ; Higa, L.Ítem Acceso Abierto Factors Affecting Biodegradation of 2-Chlorophenol by Alcaligenes sp. in Aerobic Reactors(2001) Gallego, A.; Gómez, C.; Fortunato, M.; Cenzano, L.; Rossi, S.; Paglilla, M.; Gómez Hermida, D.; Higa, L.; Korol, S.The influence of variations in carbon source concentration, cell inocula, pH, presence of other substrates, and other organisms on the biodegradation of 2-chlorophenol 2-CP was studied for ( ) Alcaligenes sp. isolated from natural sources. Assays of biodegradation were performed in batch and continuous-flow fluidized-bed aerobic reactors. Evaluation of biodegradation was performed by deter mining total phenols, chemical oxygen demand COD , and 2-CP by ultraviolet UV spectrophotometry. ( ) ()Measurement of microbial growth was carried out by the plate count method. Bioassays of acute toxicity were performed to evaluate detoxification by using Daphnia magna. Results obtained show that under batch conditions with initial inocula of 106 cells/mL the strain grew exponentially with 100, 200, and 300 ( 5 mg/L of 2-CP within 48 hr. A lag period was observed with low cell density inocula 10 cells/mL . The ) strain showed marked delay in the biodegradation of 2-CP at pH 5. Removal of target substrate from mixtures containing other carbon sources demonstrated the possibility of concurrent growth. Mineraliza tion of 2-CP was assessed by gas chromatography carried out at the end of the batch assays and at the exit of the continuous-flow reactor. The presence of other organisms bacteria, rotifers, ciliate, and ( algae that developed in the fluidized-bed reactor did not affect the efficacy of the biodegradation of )2-CP. The removal of 2-CP in the two assayed systems was over 97% in all cases. Toxicity was not detected at the exit of the continuous reactor.Ítem Acceso Abierto Remoción de As (V) de agua subterránea mediante adsorción en arenas revestidas con nitrato férrico(1° Encuentro de Investigadores en Formación en Recursos Hídricos, 2012) Rodriguez Salemi, V. ; Gómez, B. ; Marquina, L. ; Hildt, C.; Fusé, V. ; Higa, L.El objetivo de este trabajo fue obtener un medio adsorbente para la remoción de As (V) de aguas subterráneas y determinar su eficiencia. El material adsorbente consistió en arena de construcción a la cual se la sometió a un proceso de revestimiento con nitrato férrico mediante ciclos de enfriamiento y calentamiento. Se realizaron 6 tratamientos con diferentes condiciones de temperatura y humedad. La evaluación del proceso de revestimiento se realizó a partir de microscopía electrónica, análisis de composición superficial elemental y digestión ácida para la determinación del hierro total depositado sobre la superficie del mineral. Se determinó la eficiencia de remoción de As (V) a través de ensayos en batch: máxima capacidad de remoción e isotermas de adsorción. La composición elemental superficial de la arena antes del proceso de revestimiento fue de un 87.4 % de Si, mientras que después del proceso el 100 % de la superficie estaba cubierta con Fe, corroborándose la efectividad del recubrimiento ensayado. Los tratamientos que se realizaron con un mayor tiempo de exposición a 550°C presentaron mejor capacidad de adsorción de As (V) (71.9 y 66.8 % de remoción con concentraciones de As inicial de 76.5 pg/L) y menor coloración del agua al final de los ensayos. Los datos observados en los ensayos de isotermas presentaron buen ajuste al modelo de Langmuir (r2 = 0.9999) estimándose una máxima capacidad de adsorción de 25.64 pg As/g de arena tratada. La exposición de la arena tratada con nitrato férrico a 550°C durante mayor tiempo y el aumento de la relación superficie/volumen del recipiente en la etapa de secado, resultaron efectivos desde el punto de vista de la fijación del Fe y de la capacidad de adsorción de arsénico. Se obtuvieron resultados alentadores respecto de producir un medio adsorbente efectivo, económico y simple para la remoción de As.