RESUMO
Granulation of biomass is at the basis of the operation of the most successful anaerobic systems (UASB, EGSB and IC reactors) applied worldwide for wastewater treatment. Despite of decades of studies of the biomass granulation process, it is still not fully understood and controlled. "Degranulation/lack of granulation" is a problem that occurs sometimes in anaerobic systems resulting often in heavy loss of biomass and poor treatment efficiencies or even complete reactor failure. Such a problem occurred in Mexico in two full-scale UASB reactors treating cheese wastewater. A close follow-up of the plant was performed to try to identify the factors responsible for the phenomenon. Basically, the list of possible causes to a granulation problem that were investigated can be classified amongst nutritional, i.e. related to wastewater composition (e.g. deficiency or excess of macronutrients or micronutrients, too high COD proportion due to proteins or volatile fatty acids, high ammonium, sulphate or fat concentrations), operational (excessive loading rate, sub- or over-optimal water upflow velocity) and structural (poor hydraulic design of the plant). Despite of an intensive search, the causes of the granulation problems could not be identified. The present case remains however an example of the strategy that must be followed to identify these causes and could be used as a guide for plant operators or consultants who are confronted with a similar situation independently of the type of wastewater. According to a large literature based on successful experiments at lab scale, an attempt to artificially granulate the industrial reactor biomass through the dosage of a cationic polymer was also tested but equally failed. Instead of promoting granulation, the dosage caused a heavy sludge flotation. This shows that the scaling of such a procedure from lab to real scale cannot be advised right away unless its operability at such a scale can be demonstrated.
Assuntos
Queijo , Metano/química , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Anaerobiose , Biomassa , Reatores Biológicos , MéxicoRESUMO
Chlordecone (CLD) was an organochlorine insecticide whose previous use resulted in an extensive pollution of the environment with severe health effects and social consequences. A closely related compound, 5b-hydrochlordecone (5b-hydroCLD), has been searched for and often detected in environmental matrices from the geographical area where CLD was applied. The current consensus considered that its presence was not the result of a biotic or abiotic dechlorination of CLD in these matrices but rather the consequence of its presence as impurity (synthesis by-product) in the CLD released into the environment. The aim of the present study was to determine if and to what extent degradation of CLD into 5b-hydroCLD occurred in the field. To test this hypothesis, the ratios of 5b-hydroCLD and CLD concentrations in a dataset of 810 soils collected between 2006 and 2012 in Martinique were compared to the ratios measured in 3 samples of the CLD dust commercial formulations applied in the banana fields of French West Indies (FWI) and 1 sample of the technical-grade CLD corresponding to the active ingredient used in such formulations. Soil data were processed with a hierarchical Bayesian model to account for random measurement errors and data censoring. Any pathway of CLD transformation into 5b-hydroCLD occurring over the long term in FWI soils would indeed change the ratio of 5b-hydroCLD/CLD compared to what it was in the initially applied formulations. Results showed a significant increase of the 5b-hydroCLD/CLD ratio in the soils-25 times greater in soil than in commercial formulations-which suggested that natural CLD transformation into 5b-hydroCLD over the long term occurred in these soils. Results from this study may impact future decisions for the remediation of the polluted areas.
Assuntos
Biodegradação Ambiental , Clordecona/análogos & derivados , Clordecona/metabolismo , Inseticidas/metabolismo , Poluentes do Solo/metabolismo , Solo/química , Teorema de Bayes , Humanos , Martinica , Musa , Tempo , Índias OcidentaisRESUMO
Chlordecone (CHLD), a soil and foodstuff pollutant, as well as an environmentally persistent organochlorine insecticide, was used intensively in banana fields. The chlordecone uptake of three crops was measured for two types of polluted soils: allophanic and non-allophanic. The uptake is lower for allophanic soils even if their chlordecone content is higher than with non-allophanic soils. The fractal structure of the allophane aggregates was characterized at the nanoscale by small angle X-rays scattering, pore size distribution and transmission electron microscopy. We showed that clay microstructures should be an important physico-chemical factor governing the fate of chlordecone in the environment. Allophanic clays result in two counterintuitive findings: higher contaminant trappings yet lower contaminant availability. We propose that this specific, tortuous structure, along with its associated low accessibility, partly explains the low availability of chlordecone confined in allophanic soils. Capsule The fractal and tortuous microstructure of allophane clay favours the chlordecone retention in soils and disfavours the crop uptake.
Assuntos
Silicatos de Alumínio/química , Clordecona/análise , Produtos Agrícolas/química , Poluentes do Solo/análise , Solo/química , Erupções Vulcânicas , Argila , Produtos Agrícolas/crescimento & desenvolvimento , Monitoramento Ambiental , Contaminação de Alimentos/análise , Contaminação de Alimentos/prevenção & controle , Martinica , Microscopia Eletrônica de Transmissão , Porosidade , Solo/normas , Propriedades de Superfície , Difração de Raios XRESUMO
Three mesophilic bacteria (strains AMX 26B(T), UR374_02 and 12-3(T)) isolated respectively from an anaerobic digester, human urine and urban riverside soil were characterized. Cells were Gram-negative, motile, non-sporulating, straight to curved rods with one polar flagellum and had a strictly respiratory metabolism with O(2) as the preferential terminal electron acceptor. Phylogenetic analysis based on 16S rRNA gene sequences revealed that all strains clustered within the Xanthomonadaceae branch of the Proteobacteria. Isolates AMX 26B(T) and UR374_02 exhibited 100 % 16S rRNA gene sequence similarity and both were related to strain 12-3(T) (99.6 % similarity). The closest relative of all the isolates was Pseudoxanthomonas broegbernensis DSM 12573(T) (similarity 97.1-97.5 %), and they were equidistantly related to Xanthomonas species (95.4-96.6 %), Stenotrophomonas species (95.3-96.1 %) and Pseudoxanthomonas taiwanensis ATCC BAA-4040(T) (95.3-95.4 %). Chemotaxonomic and biochemical data (branched-chain cellular fatty acid pattern without C(13 : 0) iso 3-OH, ubiquinone with eight isoprenoid units, limited range of substrates used, ability to reduce nitrite but not nitrate with the production of N(2)O) supported their affiliation to the genus Pseudoxanthomonas. The results of DNA-DNA hybridization and/or phenotypic analysis allowed them to be differentiated from the two Pseudoxanthomonas species with validly published names and showed that strain 12-3(T) was genomically and phenotypically distinct from the other two isolates. On the basis of these results, two novel species of the genus Pseudoxanthomonas are proposed: Pseudoxanthomonas mexicana sp. nov., consisting of strains AMX 26B(T) (=ATCC 700993(T)=CIP 106674(T)=JCM 11524(T)) (type strain) and UR374_02 (=DSM 15133), and Pseudoxanthomonas japonensis sp. nov., consisting of strain 12-3(T) (=CCUG 48231(T)=CIP 107388(T)=JCM 11525(T)). The report of these two novel species leads to the emendation of the description of the genus Pseudoxanthomonas and the re-evaluation of the phenotype of P. broegbernensis DSM 12573(T) necessitates the emendation of its description.
Assuntos
Reatores Biológicos/microbiologia , Microbiologia do Solo , Urina/microbiologia , Xanthomonadaceae/classificação , Xanthomonadaceae/isolamento & purificação , Aerobiose , Antibacterianos/farmacologia , Técnicas de Tipagem Bacteriana , Composição de Bases , Metabolismo dos Carboidratos , DNA Bacteriano/química , DNA Bacteriano/isolamento & purificação , DNA Ribossômico/química , DNA Ribossômico/isolamento & purificação , Ácidos Graxos/análise , Ácidos Graxos/isolamento & purificação , Flagelos , Genes de RNAr , Violeta Genciana , Humanos , Dados de Sequência Molecular , Movimento , Nitritos/metabolismo , Hibridização de Ácido Nucleico , Oxigênio/metabolismo , Fenazinas , Filogenia , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Esporos Bacterianos/citologia , Stenotrophomonas/genética , Ubiquinona/análise , Ubiquinona/isolamento & purificação , Xanthomonadaceae/citologia , Xanthomonadaceae/fisiologia , Xanthomonas/genéticaRESUMO
A strictly anaerobic, moderately thermophilic, sporulating rod, designated strain Lup 33T, was isolated from an upflow anaerobic sludge blanket (UASB) reactor in Mexico. Strain Lup 33T possessed a few laterally inserted flagella, had a DNA G+C content of 32.2 mol % and grew optimally at pH 7.4 and 40 degrees C. Growth was observed at temperatures of up to 50 degrees C and was inhibited in the presence of 5% NaCl. Strain Lup 33T is heterotrophic and utilized some sugars, peptides and various single amino acids. Gelatin and casein were not used as energy sources. It performed the Stickland reaction and reduced elemental sulfur to sulfide. Acetate was the only fatty acid detected from glucose fermentation, whereas acetate together with isobutyrate and isovalerate were found as end products from peptone fermentation. Phylogenetically, strain Lup 33T branched with members of cluster XII of the order Clostridiales, with Clostridium hastiforme as the closest relative (similarity of 93%). On the basis of the phenotypic, genotypic and phylogenetic characteristics of the isolate, it is proposed as a novel species of a new genus, Sporanaerobacter acetigenes gen. nov., sp. nov. The type strain is strain Lup 33T (= DSM 13106T = CIP 106730T).
Assuntos
Acetatos/metabolismo , Esgotos/microbiologia , Bactérias Redutoras de Enxofre/classificação , Anaerobiose , Composição de Bases , Reatores Biológicos , DNA Ribossômico , Genótipo , México , Dados de Sequência Molecular , Fenótipo , Filogenia , RNA Ribossômico 16S , Análise de Sequência de DNA , Esporos Bacterianos/fisiologia , Bactérias Redutoras de Enxofre/genética , Bactérias Redutoras de Enxofre/fisiologiaRESUMO
La tolerancia al oxígeno de una biomasa anaerobia suspendida en presencia o ausencia de un sustrato primario (sacarosa) se evaluó en términos de la recuperación de la actividad metanogénica aceticlástica especial (AME) de la biomasa anaerobia y un índice de inhibición 50 por ciento (II50) asociado a la AME. Incubada en presencia de sacarosa. La biomasa anaerobia suspendida mostró resistencia a la exposición al oxígeno; la recuperación de la AME fue >45 por ciento para [O²] iniciales <20 por ciento en el espacio gaseoso, y de 10 a 12 por ciento para [O²] iniciales >20 por ciento en el espacio gaseoso. Cuando fue incubada son fuente, la biomasa suspendida fue mucho más inhibida después de la exposición al oxígeno para [O²] iniciales >20 por ciento. El efecto inhibitorio fue descrito por un II50 elevado /28,6) en contraste con un bajo II50 (5,9) cuando se incubó en presencia de sacarosa. La tolerancia de la biomasa suspendida en este trabajo parece ser del mismo orden de la biomasa anaerobia inmovilizada (gránulos anaerobios) en condiciones de incubación en presencia de sustrato: los II50 fueron 5,9 para todos anaerobios suspendidos (sacarosa) y 5,3 y 2,4 para todos granulares incubados con acetato etanol, respectivamente. La respiración aerobia heterótrofa de los lodos anaerobio floculentos incubados con sacarosa fue cerca de 4 veces mayor que la respiración basal, y la inhibición de la AME descrita por el II50 parece seguir una relación inversa con la respiración aerobia heterótrofa. La relación inversa entre II50 y respiración aerobia heterótrofa se ajustó para datos de todos granulares en la literatura y todos floculentos de este trabajo, y sigue un modelo semi-empírico general, con un coeficiente de correlación de 0,82. Esta relación parece reforzar que uno de los mecanismos principales de protección de los consorcios anaerobios contra la inhibición por oxígeno es la respiración aerobia heterótrofa