RESUMEN
Bacterially induced calcium carbonate precipitation of a Cupriavidus metallidurans isolate was investigated to develop an environmentally friendly method for restoration and preservation of ornamental stones. Biomineralization performance was carried out in a growth medium via a Design of Experiments (DoE) approach using, as design factors, the temperature, growth medium concentration, and inoculum concentration. The optimum conditions were determined with the aid of consecutive experiments based on response surface methodology (RSM) and were successfully validated thereafter. Statistical analysis can be utilized as a tool for screening bacterial bioprecipitation as it considerably reduced the experimental time and effort needed for bacterial evaluation. Analytical methods provided an insight to the biomineral characteristics, and sonication tests proved that our isolate could create a solid new layer of vaterite on marble substrate withstanding sonication forces. C. metallidurans ACA-DC 4073 provided a compact vaterite layer on the marble substrate with morphological characteristics that assisted in its differentiation. The latter proved valuable during spraying minimum amount of inoculated media on marble substrate under conditions close to an in situ application. A sufficient and clearly distinguishable layer was identified.
Asunto(s)
Carbonato de Calcio/química , Materiales de Construcción/microbiología , Cupriavidus/metabolismo , Carbonato de Calcio/metabolismo , Precipitación Química , Materiales de Construcción/análisis , Cupriavidus/química , Cupriavidus/crecimiento & desarrolloRESUMEN
Ferrous salts are commonly used as coagulants in Water Treatment Plants (WTPs). When these salts are combined with hydrogen peroxide in acidic conditions - besides coagulation - an additional Advanced Oxidation Process (Fenton's reagent) can take place. Using a response surface methodology, this paper presents the optimization of a novel treatment system constituted by Fenton's reagent (FE) and Dissolved Air Flotation (DAF) for removing 2-Methylisoborneol (MIB), geosmin and Total Suspended Solids (TSS) from raw water. FE was proven able to remove completely both micro pollutants found in the influent of a drinking water treatment plant. Moreover, higher clarification rate was achieved by coupling FE-DAF with respect FE-Sedimentation.
Asunto(s)
Aire , Cianobacterias/metabolismo , Peróxido de Hidrógeno/química , Hierro/química , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodos , Compuestos Ferrosos/química , Modelos Estadísticos , Odorantes , Oxidación-ReducciónRESUMEN
The use of bacteriophages as potential indicators of faecal pollution has recently been studied. The correlation of the number of bacterial indicators and the presence of three groups of bacteriophages, namely somatic coliphages (SOMCPH), F-RNA-specific phages (FRNAPH) and phages of Bacteroides fragilis (BFRPH), in raw and treated wastewater and sludge is presented in this study. Raw and treated wastewater and sewage sludge samples from two wastewater treatment plants in Athens were collected on a monthly basis, over a 2-year period, and analysed for total coliforms, Escherichia coli, intestinal enterococci and the three groups of bacteriophages. A clear correlation between the number of bacterial indicators and the presence of bacteriophages was observed. SOMCPH may be used as additional indicators, because of their high densities and resistance to various treatment steps.
Asunto(s)
Bacteriófagos/crecimiento & desarrollo , Enterobacteriaceae/crecimiento & desarrollo , Enterococcus/crecimiento & desarrollo , Monitoreo del Ambiente/métodos , Aguas del Alcantarillado/microbiología , Aguas del Alcantarillado/virología , Colifagos/crecimiento & desarrollo , Recuento de Colonia Microbiana , Escherichia coli/crecimiento & desarrollo , Heces/microbiología , Heces/virología , Grecia , Ensayo de Placa Viral , Microbiología del AguaRESUMEN
Accidental blast wave generation and propagation in the surroundings poses severe threats for people and property. The prediction of overpressure maxima and its change with time at specified distances can lead to useful conclusions in quantitative risk analysis applications. In this paper, the use of a computational fluid dynamics (CFD) code CFX-5.6 on dense explosive detonation events is described. The work deals with the three-dimensional simulation of overpressure wave propagation generated by the detonation of a dense explosive within a small-scale branched tunnel. It also aids at validating the code against published experimental data as well as to study the way that the resulting shock wave propagates in a confined space configuration. Predicted overpressure histories were plotted and compared versus experimental measurements showing a reasonably good agreement. Overpressure maxima and corresponding times were found close to the measured ones confirming that CFDs may constitute a useful tool in explosion hazard assessment procedures. Moreover, it was found that blast wave propagates preserving supersonic speed along the tunnel accompanied by high overpressure levels, and indicating that space confinement favors the formation and maintenance of a shock rather than a weak pressure wave.
Asunto(s)
Industria Química/métodos , Simulación por Computador , Explosiones , Ondas de Choque de Alta Energía , Imagenología Tridimensional/métodos , Modelos Químicos , Industria Química/normas , Sustancias Peligrosas/normas , Salud Laboral , Presión , Medición de RiesgoRESUMEN
Accidental release and dispersion of toxic gases were always major hazards for public health and safety that process industries had to deal with. Real terrain dispersion simulation for risk analysis purposes poses specific difficulties related to complex turbulence phenomena development, especially when obstructions are found into the flow region. In this paper, several turbulence models are tested and compared against experimental data of dense vapor dispersion, in order to decide for their suitability for simulating such flows. Computations were carried out using the computational fluid dynamics (CFD) code CFX 5.6, while experimental data were obtained from Thorney Island large scale field trials. Computational results showed good agreement with experimental measurements indicating that CFDs provide a reliable means of estimating gas dispersion in real terrains.