RESUMO

A biocomposite system was developed and tested for the removal of the azo dye Reactive Red (RR195) from wastewater. The biocomposite was synthesized using ceramic particles containing 75% alumina which were coated using chitosan cross-linked with oxalic acid. The biocomposite showed high performance at low pH (maximum adsorption capacity = 345.3mg.g-1 at pH=2.0). The physicochemical and structure characteristics of the matrix were evaluated by Z-potential, FTIR-ATR, SEM-EDS, XRD, and porosity. Langmuir sorption isotherm and pseudosecond-order model gave the best fit. The electrostatic interaction between RR195 (due to the sulfonate groups) and the free amino groups of chitosan, enabled successive desorption/regeneration cycles. The maximum removal percentage (>80%) occurred at pH=2.0 due to the cross-linking effect. Experiments at different temperatures allowed the calculation of thermodynamic parameters (ΔG, ΔS, ΔH); adsorption was spontaneous, exothermic, and enthalpy controlled. The presence of inorganic ions ([Formula: see text] ) was analyzed during the adsorption process. This novel biocomposite can be applied as a cost-effective and environmentally friendly adsorbent for anionic azo dye removal from wastewater. The application of chitosan cross-linked with oxalic acid as a coating of the ceramic support enhanced the adsorption capacity and enabled its use under acidic conditions without solubilization.

Assuntos

Quitosana , Poluentes Químicos da Água , Purificação da Água , Adsorção , Óxido de Alumínio , Compostos Azo , Corantes , Concentração de Íons de Hidrogênio , Cinética , Ácido Oxálico , Termodinâmica

RESUMO

Salted and ripened fish foods are susceptible to cause histamine poisoning. The present study focuses on microbial histamine degradation from high salted fermented fishery products to deepen our understanding about this new and growing field of research. As a result of this first study related to salted-ripened anchovies (Engraulis anchoita), fifty seven moderate and extreme halophilic microbial isolates from salt and salted-ripened anchovy processes were characterized in terms of their phenotype and histamine-degrading capacity. Only 7%-4 isolates-were able to degrade histamine. None of the histamine-degrading isolates presented proteolytic and/or lipolytic activity. One of them designated A18 was chemotactic toward histamine, an interesting property not previously reported for that chemoattractant. However, the S18 and A18 isolates, genotypically identified as Halobacterium sp. and Halomonas sp. respectively, produced indole and/or H2S, both undesirable characteristics associated to off-flavors occurrence. On the other hand, A28 and S20, identified as Halovibrio sp. and Halobacterium sp. respectively, presented desirable properties, such as cytochrome oxidase and catalase activity, and non-production of H2S and indole. These strains also showed characteristics previously reported as dominant in the ripened stage. The results are promising, and A28 and S20 may have the desirable features to improve the anchovy salting-ripening process.

Assuntos

Halobacteriales , Halomonas , Histamina , Animais , Aquicultura , Peixes , Histamina/metabolismo , RNA Ribossômico 16S , Cloreto de Sódio

RESUMO

BACKGROUND: Brewers' spent grain (BSG) is one of the most abundant by-products of the beer industry and causes serious environmental problems. Ferulic acid (FA) is an antioxidant with potential cosmeceutical applications. FA was extracted from BSG, developing a method of high extraction performance in order to be encapsulated in ultradeformable liposomes (Nanoferulic, NF). AIMS: To obtain a product with high added value such as FA, from a residue currently underused, using simple and economical chemical methods. To load FA into a nanosystem designed for the topical route, its encapsulation has the purpose to take profit from its photoprotective, anti-inflammatory, and antioxidant properties in the deep layers of the skin. METHODS: Ferulic acid was obtained from dried BSG using acid and basic treatments in series. NF was prepared by lipid film resuspension of a solution containing FA obtained from BSG. Size and Z-potential were determined. Cytotoxicity was assessed in vitro. Skin penetration was assessed by NF determination at different skin depths and by confocal microscopy. RESULTS: The yield of the extraction process was 0.43% on a dry basis. Encapsulation rendered liposomes of around 140 nm with 92% of encapsulation efficiency. No toxicity was observed in all the tested concentrations. Successful results were obtained from the regeneration studies. CONCLUSIONS: It was possible to develop a nanosystem containing FA, generating a high-value commercial input for the pharmaceutical and cosmeceutical industry. The use of BSG generated in industrial scale would help to reduce the volume of highly polluting waste.

Assuntos

Cerveja , Grão Comestível , Antioxidantes/farmacologia , Grão Comestível/química , Humanos , Regeneração

RESUMO

Cryopreservation of the germplasm for long-term periods is of great importance to maintain the genetic resource. Argentina is one of the world's highest lemon producing country. The performance of different cooling/warming rates in the cryopreservation method of Citrus limon L. Burm cv. Eureka seeds and their influence on the interval of optimal moisture content in the desiccation stage were analyzed. Water sorption isotherm was determined and modeled using D'Arcy & Watt equation; it provided important information concerning the amounts of water associated to strong, weak and multimolecular binding sites along the sorption isotherm. Seeds tolerated a wide range of desiccation conditions (0.180%), however desiccation to 0.0526 g H2O g-1 d.b. (aw = 0.0901) produced a significant loss of viability. Differential Scanning Calorimetry was used to identify the thermal transitions of lipids and water in the seed; enthalpies were used to calculate the unfrozen water fraction (0.19 g H2O g-1 d.b. corresponding to aw = 0.64). Two cooling/warming rates were tested on desiccated seeds (0.110.64 corresponding to the unfrozen water fraction. The use of higher cooling/warming rates enables a wider range of desiccation conditions (0.33

Assuntos

Citrus/crescimento & desenvolvimento , Criopreservação/métodos , Dessecação/métodos , Germinação/fisiologia , Sementes/fisiologia , Argentina , Varredura Diferencial de Calorimetria , Lipídeos/análise , Transição de Fase , Água/química

RESUMO

Individual films of polyhydroxyalkanoates (PHA) and polylactic acid (PLA) and their blends were developed by solvent casting. PHA was obtained from activated sludges from a wastewater-treatment system at a laboratory scale. This work focused on analyzing the microstructural properties and thermal behaviors of individual films of PHA and PLA as well as those of their blends. The behaviors of the biodegradation processes of the individual films and blends were examined from a microstructural point of view. ATR-FTIR spectra indicated the existence of weak molecular interactions between the polymers. The formulation of blend films improved the crystallinity of PLA; additionally, it induced the polymer-recrystallization phenomenon, because crystallized PHA acted as a PLA-nucleating agent. This phenomenon explains the improvements in the films' water-vapor-barrier properties. The blends exposed to a biodegradation process showed an intermediate behavior between PLA and PHA, leading to a consistent basis for designing systems tailored to a particular purpose.

Assuntos

Poliésteres/química , Poli-Hidroxialcanoatos/química , Temperatura Alta , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície

RESUMO

The aim of this study was to analyze the mechanisms, stoichiometry, and stability of 4-chlorophenol (4CP) biodegradation kinetics by phenol-acclimated activated sludge using open respirometry. While the removal of 4CP was higher than 98%, the removal of chemical oxygen demand (COD) ranged between 69 and 79% due to the accumulation of an intermediate metabolite. The value obtained from respirometric profiles for the stoichiometric ratio of O2 to 4CP (YO2/4CP) was 1.95 ± 0.04 mol of oxygen consumed per mol of 4CP removed. This YO2/4CP value reflected the action of the oxygenases responsible for the first steps of the aerobic oxidation of 4CP. The 4CP degradation activity decreased noticeably when successive pulses of 4CP were added to the respirometer. A mathematical model was developed to represent the aerobic biodegradation of 4CP. The fitted model adequately predicted the oxygen consumption rate, total phenols, and soluble COD concentrations as a function of time. The results presented could help to predict the dynamic of biodegradation of chlorophenols in a biological wastewater treatment system.

Assuntos

Clorofenóis/química , Fenóis/química , Esgotos/química , Biodegradação Ambiental , Reatores Biológicos , Clorofenóis/metabolismo , Cinética , Modelos Biológicos , Oxigênio/química , Fenóis/metabolismo

RESUMO

Thermal inactivation of peroxidase (POD) and lipoxygenase (LOX), both enzymes present in broccoli and Brussels sprouts, is required before freezing, to obtain high-quality precooked frozen vegetables. Rate constants of a 1st-order biphasic model for the heat-labile and heat-resistant POD and LOX isoenzymes were determined at different temperatures (75, 80, and 90 °C) and the corresponding activation energies were estimated using nonlinear regressions. In the case of Brussels sprouts, the activation energies for the resistant and labile fractions were 56.3 and 62.5 kJ/mol for POD and 63.7 and 65.8 kJ/mol for LOX, respectively. For Brussels sprouts, different precooking times were tested to analyze the effect of residual enzyme activity on quality parameters and sensory attributes, after a frozen storage of 4 mo at -20 °C. A significant reactivation of enzyme activity after frozen storage was observed (especially in the case of POD) for short precooking times (<6 min) leading to low-quality parameters at the interior zone of the vegetable. A precooking time of 6 min at 90 °C allowed an adequate inactivation of LOX and POD obtaining a high-quality final frozen vegetable. A sensory analysis confirmed the global acceptability of the product. The obtained results are relevant to define the precooking stage conditions in the production of frozen cruciferous vegetables.

Assuntos

Brassica/enzimologia , Manipulação de Alimentos/métodos , Temperatura Alta , Lipoxigenase/metabolismo , Peroxidase/metabolismo , Congelamento , Cinética , Lipoxigenase/química , Peroxidase/química

RESUMO

Chitosan particles (CH) were obtained from seafood processing wastes (shrimp shells) and physicochemically characterized; deacetylation degree of CH was measured by Infrared Spectroscopy (FTIR) and potentiometric titration; polymer molecular weight was determined by intrinsic viscosity measurements. Reticulated micro/nanoparticles of chitosan (MCH) with an average diameter close to 100nm were synthesized by ionic gelation of chitosan using tripolyphosphate (TPP), and characterized by SEM, size distribution and Zeta-potential. Detoxification capacities of CH and MCH were tested analyzing the removal of hexavalent chromium Cr(VI) from contaminated water, at different initial chromium concentrations. The effect of pH on adsorption capacity of CH and MCH was experimentally determined and analyzed considering the Cr(VI) stable complexes (anions) formed, the presence of protonated groups in chitosan particles and the addition of the reticulating agent (TPP). Chitosan crosslinking was necessary to adsorb Cr(VI) at pH<2 due to the instability of CH particles in acid media. Langmuir isotherm described better than Freundlich and Temkin equations the equilibrium adsorption data. Pseudo-second order rate provided the best fitting to the kinetic data in comparison to pseudo-first order and Elovich equations. Chemical analysis to determine the oxidation state of the adsorbed Cr, showed that Cr(VI) was adsorbed on CH particles without further reduction; in contrast Cr(VI) removed from the solution was reduced and bound to the MCH as Cr(III). The reduction of toxic Cr(VI) to the less or nontoxic Cr(III) by the reticulated chitosan micro/nanoparticles can be considered a very efficient detoxification technique for the treatment of Cr(VI) contaminated water.

Assuntos

Quitosana/química , Cromo/isolamento & purificação , Nanopartículas/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Exoesqueleto/química , Animais , Cromo/química , Indústria de Processamento de Alimentos , Resíduos Industriais , Cinética , Oxirredução , Alimentos Marinhos , Soluções , Poluentes Químicos da Água/química

RESUMO

Active starch films with glycerol and potassium sorbate were obtained by casting. Native and acetylated corn starches, as well as the mixture of them in equal proportions were used and filmogenic suspensions with pH 4.5 were also prepared. Sorbate concentration decreased during film storage due to its oxidative degradation. Active films resulted more yellow and less transparent than films without sorbate. The minimum inhibitory concentration of sorbate resulted 0.3%, regardless of the starch type and the formulation pH. The use of antimicrobial package was more effective to prevent microbial growth on food surfaces than the use of conventional methods. Additive kinetic release was neither affected by the starch type nor by the formulation pH. Sorbate diffusion process was mathematically modeled satisfactorily. Active films were able to inhibit Candida spp., Penicillium spp., S. aureus and Salmonella spp. growth. Active films extended 21% the shelf life of refrigerated cheese, regardless of the formulation pH.

Assuntos

Ácido Sórbico/farmacologia , Amido/química , Zea mays/química , Anti-Infecciosos/farmacologia , Bactérias/efeitos dos fármacos , Queijo , Cor , Preparações de Ação Retardada/farmacologia , Difusão , Fungos/efeitos dos fármacos , Fungos/crescimento & desenvolvimento , Géis , Umidade , Testes de Sensibilidade Microbiana , Soluções , Propriedades de Superfície

RESUMO

Nanocomposite films of thermoplastic corn starch (TPS) with talc particles were obtained by thermo-compression in order to study the effect of filler on structure, optical, and thermal properties. Talc increased the films rigid phase, thus their cross-sections resulted more irregular. Talc preferential orientation within matrix and good compatibility between particles and TPS was observed by SEM. Slight crystalline structure changes in TPS matrix were measured by XRD and DSC, due to talc nucleating effect. Randomly dispersed talc nanoagglomerates and individual platelets were assessed by TEM. Laminar morphology and nano-sized particles allowed that nanocomposite films were optically transparent. TPS-talc films resulted heterogeneous materials, presenting domains rich in glycerol and others rich in starch. Talc incorporation higher than 3%, w/w increased softening resistance of the nanocomposites as stated by DMA. Relaxation temperatures of glycerol-rich phase shifted to higher values since talc reduces the mobility of starch chains.

Assuntos

Nanopartículas/química , Amido/química , Talco/química , Cristalização , Glicerol/química , Plásticos/síntese química , Plásticos/química

RESUMO

Bovine plasma proteins provide the needed amino acids for the growth and development of an organism. With the purpose of preserving the native structure, related with the protein functional properties, the oligosaccharide inulin was used as protective agent and was compared with glucose and sucrose, during freeze-drying. In the present study, the thermal stability of protein was investigated as a function of type of saccharide in a concentration range of 5-15% (w/v), and at different pHs. The effect of these variables on phase transition, thermal stability and miscibility was assessed by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results of thermal protein properties (denaturation temperature and enthalpy), demonstrated that endothermic transition shifted to higher temperatures, being the stabilizing effect: inulin>glucose>sucrose. The thermal behavior suggests compatibility or interactions between the components of blends. In this way, the micrographs showed a homogeneous distribution of the different phases, corroborating the miscibility in the matrix. The unfolding process was irreversible and could be adequately described by a two-state model.

Assuntos

Proteínas Sanguíneas/química , Proteínas Alimentares , Conservação de Alimentos/métodos , Glucose/química , Inulina/química , Desnaturação Proteica/efeitos dos fármacos , Sacarose/química , Animais , Varredura Diferencial de Calorimetria/métodos , Bovinos , Liofilização/métodos , Alimento Funcional , Microscopia Eletrônica de Varredura , Transição de Fase , Temperatura , Termodinâmica

RESUMO

BACKGROUND: Three categories of seed storage behavior are generally recognized among plant species: orthodox, intermediate and recalcitrant. Intermediate seeds cannot be stored in liquid nitrogen (LN) without a previous partial dehydration process. The water content (WC) of the seeds at the moment of immersion in LN must be regarded as the most critical factor in cryopreservation. The purpose of this study was to investigate the basis of the optimal hydration status for cryopreservation of Citrus seeds: C. sinensis (sweet orange), C. paradisi (grapefruit), C. reticulata (mandarin) in LN. RESULTS: To study the tolerance to dehydration and LN exposure, seeds were desiccated by equilibration at relative humidities between 11 and 95%. Sorption isotherms were determined and modeled; lipid content of the seeds was measured. Seed desiccation sensitivity was quantified by the quantal response model. Differential scanning calorimetry (DSC) thermograms were determined on cotyledon tissue at different moisture contents to measure ice melting enthalpies and unfrozen WC. Samples of total seed lipid extract were also analyzed by DSC to identify lipid transitions in the thermograms. CONCLUSIONS: The limit of hydration for LN Citrus seeds treatment corresponded to the unfrozen WC in the tissue, confirming that seed survival strictly depended on avoidance of intracellular ice formation.

Assuntos

Agricultura/métodos , Citrus , Criopreservação , Dessecação , Sementes , Água/análise , Varredura Diferencial de Calorimetria , Citrus/química , Citrus/crescimento & desenvolvimento , Citrus paradisi/química , Citrus paradisi/crescimento & desenvolvimento , Citrus sinensis/química , Citrus sinensis/crescimento & desenvolvimento , Cotilédone/química , Cotilédone/crescimento & desenvolvimento , Difusão , Germinação , Lipídeos/análise , Lipídeos/química , Modelos Biológicos , Transição de Fase , Extratos Vegetais/química , Sementes/química , Sementes/crescimento & desenvolvimento , Especificidade da Espécie

RESUMO

The objectives of this work were: (a) to analyze the effect of alkalinity, pH and initial Fe:P molar ratio (Fe(0):P(0)) on the precipitation of orthophosphate using ferric chloride in the presence of activated sludge in order to represent conditions of simultaneous precipitation, and in exhausted wastewater to simulate conditions of post-precipitation, (b) to compare the experimental results with predictions obtained from a chemical equilibrium model, and (c) to propose a mechanistic model to determine the dose of coagulant required to achieve a given orthophosphate removal degree at constant pH. Results showed that the presence of biomass did not affect the orthophosphate precipitation; however, addition of ferric chloride caused a drop of pH to values not compatible with the normal activity of activated sludges. For this reason, the wastewater was supplemented with NaHCO(3); when 1gL(-1) NaHCO(3) was added, orthophosphate removals higher than 97% and pH above 6.2 were obtained using Fe(0):P(0)=1.9. Precipitation assays at constant pH showed that Fe(III) hydrolysis and FePO(4) precipitation reaction compete with each other. Calculations using a chemical equilibrium model (CHEAQS) predicted that ferric phosphate precipitation should not take place if pH is higher than about 7.8. However, experimental results showed that ferric phosphate precipitation occurred even at pH 9. For this reason, a mechanistic model was proposed to predict orthophosphate concentrations as a function of Fe(0):P(0) at constant pH. The model can be applied to calculate the minimum Fe(III) concentration required to achieve a given discharge limit for orthophosphate as a function of its initial concentration and pH.

Assuntos

Cloretos/química , Compostos Férricos/química , Fósforo/isolamento & purificação , Esgotos/microbiologia , Poluentes Químicos da Água/isolamento & purificação , Precipitação Química , Concentração de Íons de Hidrogênio , Resíduos Industriais/prevenção & controle , Fosfatos

RESUMO

The hexavalent chromium biological reduction constitutes a safe and economical detoxification procedure of wastewaters containing Cr(VI). However, little research has been done to evaluate Cr(VI) tolerance and reduction capacity of microbial cultures under different growth conditions. The aims of this work were (a) to evaluate the capacity of Sphaerotilus natans to reduce Cr(VI) to Cr(III) in a continuous system limited in carbon and energy source or in nitrogen source, (b) to evaluate the toxic effect of Cr(VI) on this microorganism, (c) to carry out a complete analysis of Cr(VI) reduction by S. natans not only in continuous regime but also in batch system, and (d) to model the obtained results mathematically. S. natans exhibited great resistance to Cr(VI) (19-78 mg l(-1)) and optimal growth in continuous and batch systems using a mineral medium supplemented only with citric acid as organic substrate. In carbon- and energy-limited continuous systems, a maximum percentual decrease in Cr(VI) by 13% was reached for low influent Cr(VI) concentration (4.3-5.32 mg Cr(VI)l(-1)); the efficiency of the process did not notoriously increase as the length of cellular residence time was increased from 4.16 to 50h. A nitrogen-limited continuous operation with a cellular residence time of 28.5h resulted in a Cr(VI) decrease of approximately 26-32%. In batch system, a mathematical model allowed to predict the Cr(VI) concentration as a function of time and the ratio between the initial Cr(VI) concentration and that of the biomass. High concentrations of initial Cr(VI) and biomass produced the highest performance of the process of Cr(VI) reduction reached in batch system, aspects which should be considered in detoxification strategies of wastewaters.

Assuntos

Reatores Biológicos , Cromo/metabolismo , Sphaerotilus/metabolismo , Biomassa , Cinética , Sphaerotilus/crescimento & desenvolvimento

RESUMO

In this paper respirometric techniques were used to study the effect of pH, phenol and dissolved oxygen (DO) concentrations on the phenol biodegradation kinetics by activated sludges. In addition, a mathematical model was developed to interpret the obtained respirometric curves. Closed respirometer experiments showed that phenol inhibited the respiration rate of unacclimated sludges. On the contrary, oxygen uptake rate (OUR) of phenol acclimated sludges exhibiting the typical Haldane's substrate inhibition curve. The Monod equation adequately represented the relation between OUR of acclimated biomass and DO concentration. Within the tested pH range (4-12) the oxygen saturation coefficient was independent of pH. On the contrary, the maximum OUR was strongly affected by the pH, being its maximum between 9.5 and 10.5. Open respirometer experiments shows that as pH decreased from 10.2 to 5.8, the maximum OUR also decreased, in accordance with the trend observed in the closed respirometer experiments. Although the respiration rate of phenol degrading bacteria was strongly affected by pH, a constant phenol oxidation coefficient was observed within the studied pH interval. A mathematical model was proposed to interpret the open respirometry curves. The coefficients of the model were estimated using both pseudo steady state and dynamic conditions for different biomass concentrations. The model adequately predicted the whole OUR and DO profiles as a function of time during the biodegradation of phenol under different DO conditions. The mathematical model proposed in the present work is useful for predicting transient responses such as substrate concentration and DO concentrations as a function of time in bioreactors treating phenolic wastewaters under an overload of phenolic compounds.

Assuntos

Fenol/metabolismo , Esgotos , Biodegradação Ambiental , Biomassa , Concentração de Íons de Hidrogênio , Oxigênio/metabolismo

RESUMO

Wastewaters produced by various industries may contain undesirable amounts of hexavalent chromium (Cr(VI)), as chromate and dichromate, a hazardous metal affecting flora and animals of aquatic ecosystems as well as human health. One removal strategy comprises the microbial reduction of Cr(VI) to Cr(III), a less soluble chemical species that is less toxic than Cr(VI). In this work, the ability to reduce Cr(VI) of Sphaerotilus natans, a filamentous bacterium usually found in activated sludge systems, was evaluated. In aerobic conditions, S. natans was able to efficiently reduce Cr(VI) to Cr(III) from dichromate solutions ranging between 4.5 and 80 mg Cr(VI)l(-1) in the presence of a carbonaceous source. A simultaneous evaluation of the microbial respiratory activity inhibition was also carried out to analyze the toxic effect of Cr(VI). Cr(VI) reduction by S. natans was mathematically modeled; chromium(VI) reduction rate depended on both Cr(VI) concentration and active biomass concentration. Although it is known that S. natans removes heavy metal cations such as Cr(III) by biosorption, the ability of this micro-organism to reduce Cr(VI), which behaves as an oxyanion in aqueous solutions, is a novel finding. The distinctive capacity to reduce Cr(VI) to Cr(III) than remain soluble or precipitated becomes S. natans a potential micro-organism to decontaminate wastewaters.

Assuntos

Cromo/metabolismo , Esgotos/microbiologia , Sphaerotilus/metabolismo , Poluentes Químicos da Água/metabolismo , Biomassa , Oxirredução

RESUMO

Native starch can be chemically modified to improve its functionality and to expand its uses. Modified starches were characterized and the rheological behavior of filmogenic suspensions was analyzed. The film forming capacity of different chemical modified corn starches was evaluated. Acetylated starch was selected by the characteristics of the resulted films; its optimum concentration was 5% w/w since their films exhibited the lowest water vapor permeability (WVP, 1.26×10(-10)g/msPa). The effect of glycerol as plasticizer on film properties depend on its concentration, being 1.5% w/w those that allows to obtain the lowest WVP value (1.64×10(-11)g/msPa), low film solubility in water and a more compact structure than those of unplasticized films. Mechanical behavior of plasticized acetylated starch films depends on glycerol concentration, being rigid and brittle the unplasticized ones, ductile those containing 1.5% w/w of glycerol and very flexible those with a higher plasticizer content.

RESUMO

Low-fat sausages were prepared with fresh chicken breast meat and formulated with different levels of added fat, whey protein concentrate, and hydrocolloids (xanthan and guar gums) to study the effect of composition on the stress relaxation behavior of the products. Stress relaxation experiments were conducted on precooked sausages at 25°C. Generalized Maxwell and empirical Peleg models were used to predict the stress relaxation behavior of the material. A model with seven maxwellian elements in parallel with a pure elastic element showed a very good agreement with experimental data. Results show that the proposed model satisfactorily fits the experimental data better than Peleg's model or Maxwell models with less elements. The relaxation time distribution functions were obtained. The characteristic relaxation time was shorter (2500s) for the formulations with no added fat which produced a less elastic product while the sausages with added fat showed longer characteristic relaxation time (5000s). The stress relaxation experiment differentiated the viscoelastic nature of different formulations due to reduction of fat content.

RESUMO

The combined carbon-activated sludge process has been proposed as an alternative to protect the biomass against toxic substances in wastewaters; however, the information about the effect of powdered-activated carbon (PAC) addition in activated sludge reactors for the treatment of wastewaters containing Cr(VI) is limited. The objectives of the present study were: (a) to evaluate the removal of hexavalent chromium by (i) activated sludge microorganisms in aerobic batch reactors, (ii) powdered-activated carbon, and (iii) the combined action of powdered-activated carbon and biomass; (b) to propose mathematical models that interpret the experimental results. Different Cr(VI) removal systems were tested: (S1) biomass (activated sludge), (S2) PAC, and (S3) the combined activated carbon-biomass system. A Monod-based mathematical model was used to describe the kinetics of Cr(VI) removal in the system S1. A first-order kinetics with respect to Cr(VI) and PAC respectively, was proposed to model the removal of Cr(VI) in the system S2. Cr(VI) removal in the combined carbon-biomass system (S3) was faster than both Cr(VI) removal using PAC or activated sludge individually. Results showed that the removal of Cr(VI) using the activated carbon-biomass system (S3) was adequately described by combining the kinetic equations proposed for the systems S1 and S2.

Assuntos

Carbono/química , Cromo/metabolismo , Modelos Químicos , Esgotos , Biodegradação Ambiental , Biomassa , Carbono/administração & dosagem , Cinética , Lactose , Esgotos/química , Esgotos/microbiologia , Poluentes Químicos da Água/metabolismo , Purificação da Água/métodos

RESUMO

Los objetivos del trabajo fueron analizar la degradación biológica del fenol, utilizando barros activados aclimatados y no aclimatados a ducho sustrato y determinar los parámetros cinéticos y estequiométricos correspondientes, utilizando medidas respirométricas. Por otra parte se realizaron ensayos utilizando un respirometro abierto para obtener el coeficiente de oxidación del fenol

Assuntos

Fenóis , Lodos Ativados , Purificação da Água , Argentina