Granular Diameter Research Articles

The Effect of Quorum Sensing on Mature Anaerobic Granular Sludge in Unbalanced Nitrogen Supply

This study investigated the effect of three common quorum sensing signal molecules on anaerobic granular sludge (AnGS) in unbalanced nitrogen supply. Oligotrophic nitrogen supply transiently increased the level of N-butanoyl-homoserine lactone (C4-HSL), maintaining the stability of granules by encouraging synthesis of loosely bound extracellular polymeric substance (LB-EPS). Meanwhile, the decreasing autoinducer-2 (AI-2) content and increasing diffusible signal factor (DSF) content made a combined effect on AnGS, and then it recombined the regulation from N-acyl-homoserine lactones (AHLs). In addition, eutrophic nitrogen supply enhanced C4-HSL and N-hexanoyl-homoserine lactone (C6-HSL) secretion, suggesting that it increases loose bound protein (LB-PN) level to survive in the suppression of nitrogen supply. During the unbalanced nitrogen supply process, the weaker positive effect of AI-2 and enhanced negative effect of DSF reduced relative hydrophobicity (RH) and granular strength, which made a decline of granular diameter and a degeneration of granular sludge in nitrogen oligotrophic reactor (OR) and nitrogen eutrophic reactor (ER). Therefore, the effect of the interactions among multiple signal molecules should be further elucidated in future study.

Research on the energy dissipation mechanism of nonobstructive particle dampers based on the dense granular flow theory

To study the energy dissipation mechanism of nonobstructive particle dampers (NOPDs) and provide guidance to the application of NOPDs, the dense granular flow theory was introduced to establish a quantitative energy dissipation model for NOPDs. The convection movement of the particles under vibrational excitations was studied using the discrete element method, and the Prandtl mixing length theory was adopted to modify the constitution law of dense granular flows. The pressure of the granular flow was obtained by equivalenting the vibrational excitation to a body force acted on particles. Theoretical results showed that the energy dissipation rate of the NOPD was increased with the vibration intensity and decreased with the granular diameter. It also indicated that particles near the side wall and the bottom of the damper dissipated more energy than those particles in other regions. The theoretical model was verified by simulation and experimental result. The results may provide a new approach to studying the energy dissipation mechanism of NOPD and give some guidance to enhancing the damping performance of NOPD in engineering practices.

Treatment of dyeing wastewater by MIC anaerobic reactor

A modified internal circulation (MIC) anaerobic reactor with an external hydraulic circulation system to strengthen mass transfer between sludge and substrates was used to treat dyeing wastewater and its performance was evaluated. During 110 days of operation, the MIC anaerobic reactor underwent three stages: start-up stage, improving stage, and steady stage. At the steady stage, COD removal efficiency, VFA concentration, and biogas production were approximately 85%, 158mg/L and 1.65L/Ld, respectively. The color removal efficiency was from 77% to 90% in the whole experiment. Compared with the initial granular sludge, the sludge grew bigger with the portion of the granular diameter over 2mm increasing from 77.9% to 85.5% and the suspended solid (SS) concentration increased from 66.1 to 75.9g/L. The external circulation system not only shortened the startup time of the IC reactor treating wastewater, but also improved the pollutants removal in anaerobic reactor with a reasonable hydraulic upflow velocity. However, excessive hydraulic upflow velocity (40.9m/h) caused the granular sludge disintegration and a decline in COD removal. Evaluation of the MIC reactor using the modified Stover–Kincannon model revealed the maximum removal rate constant (Umax) and saturation value constant (KB) of 31.25g/Ld and 34.94g/Ld, respectively.

Rapid start-up and improvement of granulation in SBR

BackgroundThe aim of this study is to accelerate and improve aerobic granulation within a Sequencing Batch Reactor (SBR) by cationic polymer addition.MethodsTo identify whether the polymer additive is capable of enhancing granule formation, two SBRs (R1 and R2, each 0.15 m in diameter and 2 m in height) are used by feeding synthetic wastewater. The cationic polymer with concentration of 30 to 2 ppm is added to R2, while no cationic polymer is added to R1.ResultsResults show that the cationic polymer addition causes faster granule formation and consequently shorter reactor start-up period. The polymer-amended reactor contains higher concentration of biomass with better settling ability (23% reduction in SVI15) and larger and denser granules (112% increase of granular diameter). In addition, the results demonstrate that the cationic polymer improve the sludge granulation process by 31% increase in Extracellular Polymer Substance(EPS) concentration, 7% increase in Specific Oxygen Uptake Rate(SOUR), 18% increase in hydrophobicity, and 17% reduction in effluent Mixed Liquor Suspended Solid(MLSS) concentration.ConclusionsConcludingly, it is found that using the cationic polymer to an aerobic granular system has the potential to enhance the sludge granulation process.

Physicochemical Properties of Low-Amylose Yam (Dioscorea Spp.) Starches and its Impact on α- Amylase Degradation in Vitro

Starches from four low-amylose yam cultivars, cv.Chinese yam, Bitter yam, Yampie and Akam cultivated in Jamaica were extracted and the relationship between physicochemical properties and in vitro digestibility investigated. A direct correlation between starch physicochemical properties and digestibility of the low- amylose starches was observed. Chinese and Bitter yam starches with the lowest amylose content were found to have the highest digestibility in vitro (21.27 ± 0.01 % and 18.11 ± 0.02 % respectively), while Akam and Yampie starches with higher amylose content had significantly lower percentage digestibility (p<0.05). The mean granular diameter of the starches ranged from 5.4 µm for Chinese yam to 29.58 µm for Yampie. The variations observed in the granular size may have influenced the surface properties of the starches, as Chinese yam was found to have the largest specific surface area (625.91 m2/kg) while Yampie had the lowest (117. 4 m2/kg). The digestibility of the starches was also influenced by granule diameter, specific surface area, crystalline pattern and surface-no. mean of the starches studied.

Optimum fluidization velocity of granular sludge bed for anaerobic fluidized‐bed bioreactors

AbstractBACKGROUNDThe models presented for bed optimum fluidization velocity (uopt), which was worthwhile for treatment efficiency and operation stability of anaerobic fluidized-bed bioreactors (AFB), were developed for AFB, and the anaerobic granular sludge diameter (dp) and shape were analyzed by a dynamic image analyzer.RESULTSThe results showed that the granular size from 0.05 to 0.30 cm sludge dominated the total biomass (accounted for 92.34%) in an expanded granular sludge bed reactor, the mean sphericity 0.835 and mean granular diameter 0.1606 cm were achieved. The uopt range was 0.000949–0.2851 cm s‐1 when dp was 0.05–0.30 cm, and the fluidization number was 8.43–38.77. The maximum value of 0.2851 cm s‐1 was the basic parameter for pump power matching. From parametric sensitivity analyses, uopt was significantly influenced by liquid holdup, granular diameter, granular density and liquid viscosity.CONCLUSIONAccording to the models of uopt, a better operating scheme for AFB can be provided; from parametric sensitivity analysis, further optimizing designs of such bioreactors can be achieved. © 2013 Society of Chemical Industry

Optimization of selective sludge discharge mode for enhancing the stability of aerobic granular sludge process

The selective sludge discharge mode was studied in the aerobic granular sludge reactor for improving the long-term stability of aerobic granular sludge process. Results showed that the nitrogen removal performance was obviously improved with the preliminary granulation of the bioreactor at sludge settling time of 1min after 15days. After the formation of fine granular sludge, 5–10% volume of the total granular sludge was discharged for the sludge retention time (SRT) controlling, and the removal efficiencies of NH4+–N and TN reached 95.9±2.0% and 75.3±3.0% at the SRTTotal of 5.3±0.4days, SRTGranules of 9.9±0.9days and SRTFlocs of 2.7±0.5days, respectively. The granular rate and average granular diameter of the bioreactor were stabilized at 80±5.0% and 2.3±0.3mm, respectively. The results demonstrated that a long SRT of granular sludge leads easily into the deterioration of aerobic granule, and an appropriate selective sludge discharge mode favors the stability of aerobic granular sludge process via the discharge of proportional aging granular sludge and retention of enough new-born flocs.

Factors influencing the density of aerobic granular sludge

In the present study, the factors influencing density of granular sludge particles were evaluated. Granules consist of microbes, precipitates and of extracellular polymeric substance. The volume fractions of the bacterial layers were experimentally estimated by fluorescent in situ hybridisation staining. The volume fraction occupied by precipitates was determined by computed tomography scanning. PHREEQC was used to estimate potential formation of precipitates to determine a density of the inorganic fraction. Densities of bacteria were investigated by Percoll density centrifugation. The volume fractions were then coupled with the corresponding densities and the total density of a granule was calculated. The sensitivity of the density of the entire granule on the corresponding settling velocity was evaluated by changing the volume fractions of precipitates or bacteria in a settling model. Results from granules originating from a Nereda reactor for simultaneous phosphate COD and nitrogen removal revealed that phosphate-accumulating organisms (PAOs) had a higher density than glycogen-accumulating organisms leading to significantly higher settling velocities for PAO-dominated granules explaining earlier observations of the segregation of the granular sludge bed inside reactors. The model showed that a small increase in the volume fraction of precipitates (1-5%) strongly increased the granular density and thereby the settling velocity. For nitritation-anammox granular sludge, mainly granular diameter and not density differences are causing a segregation of the biomass in the bed.

Reaction kinetics of the degradation of chloroanilines and aniline by aerobic granule

The reaction kinetics of the degradation of ClAs and AN by aerobic granules were studied in a stable sequencing airlift bioreactor (SABR). Results showed that the degradation of ClAs and AN by aerobic granules followed the Haldane equation. The maximum substrate degradation rates (Vmax) for different pollutants were as follows: AN>4-ClA>2-ClA>3-ClA>3,4-DClA, and the order of inhibition constant (Ki) was AN>3-ClA>4-ClA>2-ClA>3,4-DClA. The biodegradabilities of ClAs and AN was well relevance to their spatial parameters and thermodynamic coefficients. At the same time, the values of Vmax and Ki increased along with the granular diameter (peaked at 1.25–2.0mm), and then Ki increased but Vmax decreased. The results demonstrated that the formation of aerobic granule favours enhancing the degradability of toxic organic compounds, and controlling the granular diameter is important for optimising the performance of bioreactors.

Deposition-rate dependence of granular size distribution in Cu aggregate on liquid substrate studied by atomic force microscopy

In this article, we report an atomic force microscopy study on the microstructure and the deposition-rate dependence of granular size distribution in copper (Cu) ramified aggregates on a liquid substrate. This study shows that the ramified Cu aggregates are composed of Gaussian size distribution granules, which form immediately after the Cu atoms are deposited. The interesting phenomenon is that the mean diameter Φm of the granules exponentially decays and approaches a stable value Φc with an increase in the deposition rate f. The granular mean diameter Φm slightly changes with the time interval Δt during which the film is kept in the vacuum chamber, owing to the large diffusion coefficient of the Cu granules on the liquid substrates. The experimental behavior strongly depends on the properties of the liquid substrate.

PHYSICAL PROPERTIES OF LARGE AND SMALL GRANULES IN SOLAR QUIET REGIONS

The normal mode observations of seven quiet regions obtained by the Hinode spacecraft are analyzed to study the physical properties of granules. An artificial intelligence technique is introduced to automatically find the spatial distribution of granules in feature spaces. In this work, we investigate the dependence of granular continuum intensity, mean Doppler velocity, and magnetic fields on granular diameter. We recognized 71,538 granules by an automatic segmentation technique and then extracted five properties: diameter, continuum intensity, Doppler velocity, and longitudinal and transverse magnetic flux density to describe the granules. To automatically explore the intrinsic structures of the granules in the five-dimensional parameter space, the X-means clustering algorithm and one-rule classifier are introduced to define the rules for classifying the granules. It is found that diameter is a dominating parameter in classifying the granules and two families of granules are derived: small granules with diameters smaller than 144, and large granules with diameters larger than 144. Based on statistical analysis of the detected granules, the following results are derived: (1) the averages of diameter, continuum intensity, and Doppler velocity in the upward direction of large granules are larger than those of small granules; (2) the averages of absolute longitudinal, transverse, and unsigned flux density of large granules are smaller than those of small granules; (3) for small granules, the average of continuum intensity increases with their diameters, while the averages of Doppler velocity, transverse, absolute longitudinal, and unsigned magnetic flux density decrease with their diameters. However, the mean properties of large granules are stable; (4) the intensity distributions of all granules and small granules do not satisfy Gaussian distribution, while that of large granules almost agrees with normal distribution with a peak at 1.04 I 0.

Feasibility and influence factors of a new silver salt method for determination of arsenic in drinking water

Objective To investigate the feasibility and influence factors of a new silver salt method for determination of arsenic in drinking water. Methods Arsenic was determined at different reaction temperature,acidity, specification and addition of zinc granular, fill weight of lead acetate cotton, and the effect of these factors on assay results was observed. Arsenic in drinking water was determined in accordance with standard test methods (GB/T 5750.6) of the new silver method. Results The recoveries of the arsenic were 75.3％ - 93.6％(F =9.21,P ＜ 0.01 ) with reaction temperature at 10 - 30 ℃, and the best reaction temperature was 25 ℃. The recoveries of the arsenic ranged from 80.3％ - 91.6％(F =4.67, P＜ 0.05) when sulfuric acid was 3.0 - 6.0 ml and the best value was 5.0 ml. The recoveries of the honeycomb structural zinc granular(diameter 0.2 - 0.3, 0.3 - 0.4 mm) and button zinc granular were 87.2％, 90.7％ and 83.0％, respectively; the best specification was 0.3 - 0.4 mm. The recoveries of zinc granular weight(3 - 5 g ) were 74.6％ - 91.7％, respectively; the best was 5 g. The recoveries ranged from 79.6％ - 91.3％ with fill weight of lead acetate cotton at 25 - 100 mg, the best fill weight was 50 mg.The recoveries of the arsenic were 90.7％, 92.5％, 81.5％ and 74.2％ with lead acetate cotton length at 0.5 - 2.0 cm,and the best loose-tight degree was 1.0 cm. The stability time of arsine solution was 5.0, 4.0, 2.5 h with corresponding temperature at 20, 25, 30 ℃, respectively. Conclusions In order to ensure precision and accuracy of the measurement, it is necessary to control reaction temperature, acidity, specification and addition of zinc granular free from arsenic, fill weight of lead acetate cotton and loose-tight degree in the reaction system. Key words: Drinking; Arsenic; New silver salt method; Factors

A quantitative analysis on the energy dissipation mechanism of the non-obstructive particle damping technology

The non-obstructive particle damping (NOPD) technology has been recently developed from particle damping and impact damping technologies. In this paper, a quantitative analysis of the dissipation mechanism of NOPD based on a statistical theory is investigated for the first time to our knowledge. Under high-frequency vibrations, the dense granular motion of NOPD is very similar to turbulence. Thus, Kolmogorov's hypothesis in turbulence is adopted to describe the energy spectral density and velocity correlation function of the particles in the NOPD technology. It is shown that the NOPD's mean energy dissipation (per unit mass) increases with either the granular diameter or the volume ratio of the dense granular flow. The quantitative model for the NOPD technology presented in the paper should be useful in possible engineering applications of vibration reduction.

Study on Short-Cut Nitrification Aerobic Granular Sludge Cultivation and Carbon-Nitrogen Removal

Acclimation of short-cut nitrification aerobic granular sludge with aerobic granular sludge and nitrification sludge as seed sludge in a sequencing batch reactor(SBR) by controlling the pH, influent ammonia concentration, temperature and other conditions. Experimental results showed that the short-cut nitrification aerobic granular sludge with high ammonia and COD removal rate (95%) was formed successfully, and SBR can run long-term stably. DO at 6.0~8.0mg/L when the nitrosation rate remained stable at 50% ~ 60%, and lower DO levels within the reactor (2.0~3.0mg/L) nitrosation rates of up to 90%. Mature short-cut nitrification aerobic granular sludge average diameter of 2~3mm in between, MLSS of up to 10.162g/L, SVI minimum up to 22.63ml/g, moisture content is only 81.93%, total nitrogen removal rate of 40%, and carbon-nitrogen removal capability.

A comparative investigation of the packing and flow properties of sweet potato (Ipomoea batatas) starches and their potential use in solid dosage formulations

AbstractA comparative evaluation of the flow and packing properties of starch products extracted from three sweet potato (Ipomoea batatas) cultivars grown in Jamaica was done with a view to assessing their suitability as excipients in solid dosage formulations. Significant differences were observed in the properties of the starches obtained from the different sweet potato cultivars (p&lt;0.05). The mean granular diameter ranged from 13.4 ± 0.42 (Eustace) to 20 ± 0.85 µm (Clarendon). Clarendon starch was found to be the least cohesive and bulkiest with Compressibility Index (CI) of 32.69 ± 0.28%, angle of internal flow (θi) of 12.70 ± 0.12° and maximum volume reduction (a) of 35.65 ± 1.02%, while Eustace was the most cohesive and least bulky with CI values of 37.74 ± 1.06%, θi of 19.68 ± 0.22°, and a of 43.60 ± 0.95%. The starch powders had similar bulk densities and packing fraction (p&gt;0.05). All other fundamental properties calculated from the projected mean diameter including surface mean diameter (dvs), Heywood equivalent diameter (de) and specific surface (Sw) varied significantly (p&lt;0.05) in a cultivar‐dependent manner but with no consistent pattern of variation among cultivars. The results indicate intravarietal variations in the packing and cohesive properties of the starches studied which may be a result of variations in the fundamental properties of the granules. These differences in properties may prove significant when predicting the behaviour of starches during handling and pharmaceutical formulations.

Effect of granular size on the angle of repose in the chute

Avalanche in the chute has been studied to examine how the sizes of granules affect the angle of repose θ r when the width of the chute is fixed. The results show that the angle of repose in the chute has exponential decay with λ, which is the reciprocal of granular diameter d. The fluctuation of the angle of repose is also studied during the chute being tilted, and the results indicate that the fluctuation of the angle of repose increases with the increase of granular diameter d.

Reciprocating extrusion of in situ Mg 2Si reinforced Mg-Al based composite

Mg 2 Si reinforced Mg-Al based composite with high amount of silicon was prepared by permanent mould casting, and then extruded by reciprocating extrusion (RE) after the composite was processed by homogenization heat treatment. The effect of RE processing on the morphology and size of Mg 2 Si and the mechanical properties of the composite were investigated, to develop new ways to refine the Mg 2 Si phase and improve its shape. The result showed that RE was very useful in refining the Mg 2 Si phase. The more the RE processing passes, the better the refining effect would be. Moreover, the uniform distribution of Mg 2 Si phases would be more in the composite. After the composite was processed by RE for 12 passes, most Mg 2 Si phases were equiaxed, with granular diameter below 20 μm, and distributed uniformly in the matrix of the composite. The mechanical properties of the composite could be increased prominently by RE processing, and were much higher than that in the as-cast state. As the temperature rises, the tensile strength is reduced. For the composite RE processed for 12 passes, the tensile strength, yield strength, and elongation are 325.9 MPa, 211.4 MPa, and 3.3% at room temperature, whereas, 288.2 MPa, 207.7 MPa, and 7.8%, respectively, at 150°C. In comparison with the properties at room temperature, the tensile strength and yield strength are high and only decrease by 11.6% and 1.8% at 150°C. The Mg 2 Si reinforced Mg-Al based composite possesses good heat resistance at 150°C. The excellent resistance to effect of heat is attributed to the high melting temperature and good thermal stability of fine Mg 2 Si phases, which are distributed uniformly in the composite, and effectively hinder the grain boundary gliding and dislocation movement.

Surface properties of yam ( Dioscorea sp.) starch powders and potential for use as binders and disintegrants in drug formulations

A comparative investigation of the surface properties of starch powders from three species of yam ( Dioscorea spp.) was conducted, using corn starch BP as reference standard, with a view to assessing their usefulness as ingredients of tablets/capsule formulations. Significant differences were observed in the physicomechanical properties of the starches obtained from the various yam species. Granular diameter ranged from 5.4 μm (Chinese yam) to 34.5 μm (Round leaf yellow yam). Corn starch BP has a mean granular diameter of 12.3 μm. Chinese yam starch had the highest specific surface area (625.91 m 2/kg) while Round leaf yellow yam had the lowest (117. 4 m 2/kg); corn starch BP has a specific surface area of 232 m 2/kg. The surface tension of the starch mucilage also varied significantly with Bitter yam having the lowest (44.56 mN/m) and Round leaf yellow yam the highest (54.00 mN/m); corn starch had a surface tension of 62 mN/m. X-ray powder diffraction revealed three distinct crystalline patterns: Bitter yam and corn starch displayed the type A while Round leaf yellow yam and Chinese yam displayed the types B and C patterns respectively. In moisture adsorption, all the starches studied displayed monolayer adsorption profiles with rate order of moisture adsorption ranging from 0.92 mg%/h for Chinese yam to 1.07 mg%/h for Round leaf yellow yam starch. Since co-formulated materials will react or interact at the interface, the variations observed in the surface properties suggest a potential for significant botanical specie-dependent differences in performance of starch powder in formulated dosage forms.

Physicochemical, thermal properties and microstructure of six varieties of taro ( Colocasia esculenta L. Schott) flours and starches

Taro ( Colocasia esculenta L. Schott) flours were prepared from six varieties of taro corms coded as RIN, RIE, CN, CE, KW1 and KW2. Starch yields prepared from the flours varied between 66.5% for KW2 to 86.6% for RIE. The proteins content varied from 2.9% for KW1 to 4.9% for CN in the flours. Taro starch had irregular, polygonal shapes and small granular sizes. A wide variation was observed in the granular diameter of each of the starch samples and between the samples. The amylose contents varied from 14.7 ± 1.64% to 30.85 ± 0.63% as determined by the DSC method. The taro starch contained 0.2–0.6% lipids and 2% ash. The onset gelatinisation temperatures of the taro flours varied from 55.2 to 65.49 °C, whereas those of the starches are between 48.08 ± 2.46 for KW2 and 64.37 ± 2.35 °C for KW1. Retrogradation of the starches and the flours, as measured by their enthalpy changes, appeared to vary significantly between the varieties. The water absorption capacity varied from 240% to 470% and from 60% to 250% for the flours and starches samples, respectively. Taro flours had higher solubility index than their starch counterparts. Among the varieties, RIN and CE starches had the highest solubility whereas KW1 starch had the lowest. The sorption study also revealed the high ability of the taro flours to absorb water compared to their starch components.

Equivalent deformation properties of ground treated with rammed granular piles

The effect of the granular piles installation on the modifications induced over the deformation properties of in situ soil is studied. Parameters, such as modulus of deformation and shear modulus are considered to vary with distance from rammed granular pile (RGP). Densification effect on ground adjacent to rammed granular piles from published case studies is collected and collated to propose the variations in deformation moduli of the ambient soil. Two types of variations namely linear and exponential are proposed. Equivalent deformation properties are then determined from the expressions derived for the proposed variations. Dependence of equivalent deformation properties of ground treated with RGP on the area ratio (factor representing the geometry of granular piles, i.e., diameter and spacing), the elastic modulus of the granular pile material and the magnitude and rate of decrease on the deformation modulus of the ambient soil with distance was quantified. A settlement problem is considered and verified to validate the use of the method based on the equivalent deformation properties.