Refractory castables are composed of fractions of fine to fairly coarse particles. The fine fraction is constituted primarily of raw materials and calcium aluminate cement, which becomes hydrated, forming chemical bonds that stiffen the concrete during the curing process. The present study focused on an evaluation of several characteristics of two refractory castables with similar chemical compositions but containing aggregates of different sizes. The features evaluated were the maximum load, the fracture energy, and the ""relative crack-propagation work"" of the two castables heat-treated at 110, 650, 1100 and 1550 degrees C. The results enabled us to draw the following conclusions: the heat treatment temperature exerts a significant influence on the matrix/aggregate interaction, different microstructures form in the castables with temperature, and a relationship was noted between the maximum load and the fracture energy. (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved.; FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo)[2001/04324-8]; CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico)[304980/2003-0]; CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico)[301073/2006-6]; Universal Project[470504/2004-8]; Senior Post-Doctoral fellowship[150038/2006-2]; CAPES for Procad; Probal project[258/07]
An investigation was performed regarding the application of a mechanically stirred anaerobic sequencing batch biofilm reactor containing immobilized biomass on inert polyurethane foam (AnSBBR) to the treatment of soluble metalworking fluids to remove organic matter and produce methane. The effect of increasing organic matter and reactor fill time, as well as shock load, on reactor stability and efficiency have been analyzed. The 5-L AnSBBR was operated at 30 A degrees C in 8-h cycles, agitation of 400 rpm, and treated 2.0 L effluent per cycle. Organic matter was increased by increasing the influent concentration (500, 1,000, 2,000, and 3,000 mg chemical oxygen demand (COD)/L). Fill times investigated were in the batch mode (fill time 10 min) and fed-batch followed by batch (fill time 4 h). In the batch mode, organic matter removal efficiencies were 87%, 86%, and 80% for influent concentrations of 500, 1,000, and 2,000 mgCOD/L (1.50, 3.12, and 6.08 gCOD/L.d), respectively. At 3,000 mgCOD/L (9.38 gCOD/L.d), operational stability could not be achieved. The reactor managed to maintain stability when a shock load twice as high the feed concentration was applied, evidencing the robustness of the reactor to potential concentration variations in the wastewater being treated. Increasing the fill time to 4 h did not improve removal efficiency...
Currently, there is an increasing demand for the production of biodiesel and, consequently, there will be an increasing need to treat wastewaters resulting from the production process of this biofuel. The main objective of this work was, therefore, to investigate the effect of applied volumetric organic load (AVOL) on the efficiency, stability, and methane production of an anaerobic sequencing batch biofilm reactor applied to the treatment of effluent from biodiesel production. As inert support, polyurethane foam cubes were used in the reactor and mixing was accomplished by recirculating the liquid phase. Increase in AVOL resulted in a drop in organic matter removal efficiency and increase in total volatile acids in the effluent. AVOLs of 1.5, 3.0, 4.5 and 6.0 g COD L(-1) day(-1) resulted in removal efficiencies of 92%, 81%, 67%, and 50%, for effluent filtered samples, and 91%, 80%, 63%, and 47%, for non-filtered samples, respectively, whereas total volatile acids concentrations in the effluent amounted to 42, 145, 386 and 729 mg HAc L(-1), respectively. Moreover, on increasing AVOL from 1.5 to 4.5 g COD L(-1) day(-1) methane production increased from 29.5 to 55.5 N mL CH(4) g COD(-1). However, this production dropped to 36.0 N mL CH(4) g COD(-1) when AVOL was increased to 6.0 g COD L(-1) day(-1)...
The aim of this work was to investigate the effect of different feeding times (2, 4, and 6 h) and organic loading rates (3, 6 and 12 gCOD l(-1) day(-1)) on the performance of an anaerobic sequencing batch reactor containing immobilized biomass, as well as to verify the minimum amount of alkalinity that can be added to the influent. The reactor, in which mixing was achieved by recirculation of the liquid phase, was maintained at 30 +/- 1A degrees C, possessed 2.5 l reactional volume and treated 1.5 l cheese whey in 8-h cycles. Results showed that the effect of feeding time on reactor performance was more pronounced at higher values of organic loading rates (OLR). During operation at an OLR of 3 gCOD l(-1) day(-1), change in feeding time did not affect efficiency of organic matter removal from the reactor. At an OLR of 6 gCOD l(-1) day(-1), reactor efficiency improved in relation to the lower loading rate and tended to drop at longer feeding times. At an OLR of 12 gCOD l(-1) day(-1) the reactor showed to depend more on feeding time; higher feeding times resulted in a decrease in reactor efficiency. Under all conditions shock loads of 24 gCOD l(-1) day(-1) caused an increase in acids concentration in the effluent. However, despite this increase...
Safe application of the anaerobic sequencing biofilm batch reactor (ASBBR) still depends on deeper insight into its behavior when faced with common operational problems in wastewater treatments such as tolerance to abrupt variations in influent concentration, so called shock loads. To this end the current work shows the effect of organic shock loads on the performance of an ASBBR, with a useful volume of 5 L, containing 0.5-cm polyurethane cubes and operating at 30 degrees C with mechanical stirring of 500 rpm. In the assays 2 L of two types of synthetic wastewater were treated in 8-h cycles. Synthetic wastewater I was based on sucrose-amide-cellulose with concentration of 500 mg COD/L and synthetic wastewater II was based on volatile acids with concentration ranging from 500 to 2000 mg COD/L. Organic shock loads of 2-4 times the operation concentration were applied during one and two cycles. System efficiency was monitored before and after application of the perturbation. When operating with concentrations from 500 to 1000 mg COD/L and shock loads of 2-4 times the influent concentration during one or two cycles the system was able to regain stability after one cycle and the values of organic matter, total and intermediate volatile acids...
Neste trabalho avaliou-se o desempenho de um reator anaeróbio operado em batelada seqüencial e contendo biomassa imobilizada (ASBBR) em espuma de poliuretano quando submetido a diferentes tempos de alimentação e cargas orgânicas volumétricas, além da aplicação de cargas de choque orgânicas. O reator, com mistura por recirculação da fase líquida e mantido à 30 ± 1 ºC, tratou soro de queijo reconstituído e possuiu 2,5 L de volume reacional. Os resultados mostraram que o tempo de alimentação utilizado exerceu maior influência sobre o desempenho do reator para maiores valores de carga orgânica volumétrica. Durante a operação com carga orgânica volumétrica de 3 gDQO/L.d, a alteração do tempo de alimentação não influenciou na eficiência de remoção de matéria orgânica filtrada, que foi de 98%. Sob carregamento orgânico volumétrico de 6 gDQO/L.d, verificou-se tendência de queda daquela variável para maiores tempos de enchimento: 99, 98 e 97%, para tempos de alimentação de 2, 4 e 6 horas, respectivamente. Na operação com carga orgânica volumétrica de 12 gDQO/L.d, o aumento do tempo de alimentação resultou em queda mais significativa da eficiência de remoção de matéria orgânica filtrada: 97...
Two shock loads of a detergent (shock 1 with 0.15 gCOD/L during 56 h, and shock 2 with 0.30 gCOD/L during 222 h) were applied in a lab-scale EGSB reactor with 1.5 gCOD/L of ethanol.
Quantitative image analysis and methanogenic activity measurements were used to characterize the surfactant effects.
The COD removal efficiency was unaffected with 0.15 g/L of detergent. However, 88 h after exposure to 0.30 g/L of detergent the COD removal efficiency decreased drastically.
In the first 8h of operation of shock 1, the specific methanogenic activity (SMA) was slightly stimulated and decreased afterwards, being recovered 5 days after the end of exposure time.
Concerning the shock 2, the SMA was immediately and persistently reduced during the exposure time.
Although, the SMA in the presence of H2/CO2 and ethanol were recovered, no improvement was detected in the SMA in the presence of acetate and propionate through the recovery phase.
Acetoclastic bacteria are more sensitive to the toxic effects of surfactant, and, the effects are dependent of surfactant concentration and exposure time.
The dynamic evolution of filaments length, aggregates area and aggregates density were well defined by the image analysis descriptors. The ratio filament length / total aggregate area proved to be a good
washout early warning indicator...
The use of quantitative image analysis techniques, together with physiological information might be
used to monitor and detect operational problems in advance to reactor performance failure. Industrial organic
solvents such as white spirit are potentially harmful to granular sludge. In preliminary batch assays, 33 mg.L?¹ of solvent caused 50% relative biomass activity loss. In an Expanded Granular Sludge Blanket reactor fed
with 40 mg.L?¹ of solvent, during 222 h, the reactor performance seemed to be unaffected, presenting COD
removal efficiency constantly above 95 %. However, in the first hours of exposure the specific acetoclastic
and the specific hydrogenotrophic methanogenic activities decreased by 29 and 21 %, respectively. The %
of projected aggregates area with equivalent diameter (Deq) higher than 1 mm decreased from 81 to 53 %
and consequently the % of projected area of small aggregates increased. The average equivalent diameter
of the aggregates larger than 2 mm decreased as well as the settling velocity, showed that the granules
experienced fragmentation phenomenon caused by the solvent shock load. The ratio between total filaments
length and total aggregates projected area (LfA) increased 2 days before effluent volatile suspended solids...
Detergents and solvents are included in the list of compounds that can be inhibitory or toxic to anaerobic digestion processes. Industrial cleaning stages/processes produce vast amounts of contaminated wastewater. In order to optimize the control of these wastewaters it is important to know and predict the effects on the activity and physical properties of anaerobic aggregates in an early stage. Datasets gathering morphological, physiological and reactor performance information were created from three toxic shock loads (SL1 – 1.6 mgdetergent/L; SL2 – 3.1 mgdetergent/L; SL3 – 40 mgsolvent/L). The use of Principal Component Analysis (PCA) allowed the visualization of the main effects caused by the toxics, by
clustering the samples according to its operational phase, exposure or recovery. The morphological
parameters showed to be sensitive enough to detect the operational problems even before the COD removal efficiency decreased. Its high loadings in the plane defined by the first and second principal components, which gathers the higher variability in datasets, express the usefulness of monitor the biomass morphology in order to achieve a suitable control of the process. PCA defined a new latent variable t, gathering the most relevant variability in dataset...
Principal component analysis (PCA) was applied to datasets gathering morphological, physiological and reactor performance information, from three toxic shock loads (SL1 – 1.6 mgdetergent/L; SL2 – 3.1 mgdetergent/L; SL3 – 40 mgsolvent/L) applied in an expanded granular sludge bed (EGSB) reactor. The PCA allowed the visualization of the main effects caused by the toxics, by clustering the samples according to its operational phase, exposure or recovery. The aim was to investigate the variables or group of variables that mostly contribute for the early detection of operational problems. The morphological parameters showed to be sensitive enough to detect the operational problems even before the COD removal efficiency decreased. As observed by the high loadings in the plane defined by the first and second principal components. PCA defined a new latent variable t, gathering the most relevant variability in dataset, that showed an immediate variation after the toxics were fed to the reactors. t varied 262%, 254% and 80%, respectively, in SL1, SL2 and SL3. The high loadings/weights of the morphological parameters associated with this new variable express its influence in shock load monitoring and control, and consequently in operational problems recognition.; Fundação para a Ciência e a Tecnologia (FCT) -Bolsa SFRH/BD/13317/2003...
The wide fluctuations in flow rate and the presence of toxic compounds can damage
the high efficiency of high-rate anaerobic granular sludge reactors. As earlier these
disturbances are detected, more accurate would be the corrective actions, and less
damage will be caused to the microorganisms involved in the process. The use of
Principal Component Analysis (PCA) determined a latent variable, combining a
weighted sum of operational, physiological, and morphological data, which showed
high sensitivity to recognize the operational problems occurred when four organic
loading disturbances and three toxic shock loads were applied to Expanded Granular
Sludge Bed reactors. The high loadings/weights linked with the morphological
parameters, specially the aggregates size distribution (>0.1, >1) and filaments length
dynamics (TL/VSS), obtained using quantitative image analysis techniques, illustrate
the usefulness of monitor the structural changes of the anaerobic granular sludge. The
application of PCA chemometric tool to dataset gathering information from all
disturbances allowed the differentiation between organic loading and toxic shock
disturbances, as well as the main effects caused by each class of disturbance.; Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/13317/2003...
The use of quantitative image analysis techniques, together with physiological information might be used to monitor and detect operational problems in advance to reactor performance failure. Industrial organic solvents, such as White Spirit, are potentially harmful to granular sludge. In preliminary batch assays, 33 mg L?1 of solvent caused 50% relative biomass activity loss. In an expanded granular sludge blanket reactor fed with 40 mg L?1 of solvent, during 222 h, the reactor performance seemed to be unaffected, presenting COD removal efficiency consistently >95%. However, in the last days of exposure, the biogas production and the methane content were inhibited. Afterwards, already during recovery phase, the COD removal efficiency decreased to 33%, probably because the reactor was underloaded and the biomass became saturated in solvent only at this stage. In the first hours of exposure the specific acetoclastic and the specific hydrogenotrophic methanogenic activities decreased 29% and 21%, respectively. The % of aggregates projected area with equivalent diameter (Deq) > 1 mm decreased from 81% to 53%. The mean Deq of the aggregates ?0.2 mm decreased, as well as the settling velocity, showing that the granules experienced fragmentation phenomenon caused by the solvent shock load. The ratio between total filaments length and total aggregates projected area (LfA) increased 2 days before effluent volatile suspended solids...
Knowing that wide fluctuations in flow rate and presence of toxic compounds can damage the high efficiency
of high-rate anaerobic granular sludge reactors, the use of Principal Component Analysis (PCA)
to detect organic and toxic disturbances was tested. As earlier these disturbances are detected, more
accuratewould be the corrective actions, and less damage will be caused to the microorganisms involved
in the process. The PCA determined a latent variable, combining a weighted sum of operational, physiological,
and morphological data, which showed high sensitivity to recognize the operational problems
occurred when four organic loading disturbances (OLDs) and three toxic shock loads (TSLs) were applied
to Expanded Granular Sludge Bed (EGSB) reactors. The high loadings/weights linked with the morphological
parameters, specially the aggregates size distribution (>0.1, >1), obtained using quantitative image
analysis techniques, demonstrate the usefulness of monitor the anaerobic granular sludge structural
changes. The application of PCA chemometric tool to dataset gathering information from all disturbances
allowed the differentiation between organic loading and toxic shock disturbances, as well as the main
effects caused by each class of disturbance.; Fundação para a Ciência e a Tecnologia (FCT)
Bioaugmentation of bioreactors focuses on the removal of xenobiotics, with little attention typically paid to the recovery of disrupted reactor functions such as ammonium-nitrogen removal. Chloroanilines are widely used in industry as a precursor to a variety of products and are occasionally released into wastewater streams. This work evaluated the effects on activated-sludge reactor functions of a 3-chloroaniline (3-CA) pulse and bioaugmentation by inoculation with the 3-CA-degrading strain Comamonas testosteroni I2 gfp. Changes in functions such as nitrification, carbon removal, and sludge compaction were studied in relation to the sludge community structure, in particular the nitrifying populations. Denaturing gradient gel electrophoresis (DGGE), real-time PCR, and fluorescent in situ hybridization (FISH) were used to characterize and enumerate the ammonia-oxidizing microbial community immediately after a 3-CA shock load. Two days after the 3-CA shock, ammonium accumulated, and the nitrification activity did not recover over a 12-day period in the nonbioaugmented reactors. In contrast, nitrification in the bioaugmented reactor started to recover on day 4. The DGGE patterns and the FISH and real-time PCR data showed that the ammonia-oxidizing microbial community of the bioaugmented reactor recovered in structure...
Two naturally selected microbial populations were maintained under continuousflow conditions with glucose or magnesium growth-limiting. The reactors were subjected to shock loads by changing the influent substrate from L-lysine to a mixture of L-lysine and glucose, L-lysine and fructose, or L-lysine and ribose. During the subsequent transient state, the following parameters were examined: lysine chemical oxygen demand (COD), carbohydrate COD, total COD, biological solids concentration, cell protein, enzymatic capability (lysine-degrading enzymes), and the rate of lysine removal. The carbohydrate was then removed from the influent and the same parameters were examined until a new steady state was established. In all cases, glucose and fructose caused a significant repression of the synthesis of lysine-degrading enzymes, resulting in a decrease in the enzymatic capability of the cells. In the carbon-limited reactor, the faster the flow rate, the greater was the repression, whereas, in the magnesium-limited reactor, the slower the flow rate, the greater was the repression. The introduction of ribose into the reactors caused an initial increase in lysine enzymatic capability followed by a slight repression when ribose degradation started.
There is strong experimental evidence for the existence of strange modes of failure of microelectromechanical systems (MEMS) devices under mechanical shock and impact. Such failures have not been explained with conventional models of MEMS. These failures are characterized by overlaps between moving microstructures and stationary electrodes, which cause electrical shorts. This work presents modeling and simulation of MEMS devices under the combination of shock loads and electrostatic actuation, which sheds light on the influence of these forces on the pull-in instability. Our results indicate that the reported strange failures can be attributed to early dynamic pull-in instability. The results show that the combination of a shock load and an electrostatic actuation makes the instability threshold much lower than the threshold predicted, considering the effect of shock alone or electrostatic actuation alone. In this work, a single-degree-of-freedom model is utilized to investigate the effect of the shock–electrostatic interaction on the response of MEMS devices. Then, a reduced-order model is used to demonstrate the effect of this interaction on MEMS devices employing cantilever and clamped–clamped microbeams. The results of the reduced-order model are verified by comparing with finite-element predictions. It is shown that the shock–electrostatic interaction can be used to design smart MEMS switches triggered at a predetermined level of shock and acceleration.
Microorganisms capable of generating electricity in microbial fuel cells (MFCs) have gained increasing interest. Here fourteen exoelectrogenic bacterial strains were isolated from the anodic biofilm in an MFC before and after copper (Cu) shock load by Hungate roll-tube technique with solid ferric (III) oxide as an electron acceptor and acetate as an electron donor. Phylogenetic analysis of the 16S rRNA gene sequences revealed that they were all closely related to Enterobacter ludwigii DSM 16688T within the Enterobacteriaceae family, although these isolated bacteria showed slightly different morphology before and after Cu shock load. Two representative strains R2B1 (before Cu shock load) and B4B2 (after Cu shock load) were chosen for further analysis. B4B2 is resistant to 200 mg L?1 of Cu(II) while R2B1 is not, which indicated the potential selection of the Cu shock load. Raman analysis revealed that both R2B1 and B4B2 contained c-type cytochromes. Cyclic voltammetry measurements revealed that strain R2B1 had the capacity to transfer electrons to electrodes. The experimental results demonstrated that strain R2B1 was capable of utilizing a wide range of substrates, including Luria-Bertani (LB) broth, cellulose, acetate, citrate, glucose...
The objective of this effort is to develop a computational methodology to capture the startup side load physics and to anchor the computed aerodynamic side loads with the available data from a regeneratively cooled, high-aspect-ratio nozzle, hot-fired at sea level. The computational methodology is based on an unstructured-grid, pressure-based, reacting flow computational fluid dynamics and heat transfer formulation, a transient 5 s inlet history based on an engine system simulation, and a wall temperature distribution to reflect the effect of regenerative cooling. To understand the effect of regenerative wall cooling, two transient computations were performed using the boundary conditions of adiabatic and cooled walls, respectively. The results show that three types of shock evolution are responsible for side loads: generation of combustion wave; transitions among free-shock separation, restricted-shock separation, and simultaneous free-shock and restricted shock separations; along with the pulsation of shocks across the lip, although the combustion wave is commonly eliminated with the sparklers during actual test. The test measured two side load events: a secondary and lower side load, followed by a primary and peak side load. Results from both wall boundary conditions captured the free-shock separation to restricted-shock separation transition with computed side loads matching the measured secondary side load. For the primary side load...