scholarly journals Association of Cryptosporidium with bovine faecal particles and implications for risk reduction by settling within water supply reservoirs

2006 ◽  
Vol 4 (1) ◽  
pp. 87-98 ◽  
Author(s):  
Justin D. Brookes ◽  
Cheryl M. Davies ◽  
Matthew R. Hipsey ◽  
Jason P. Antenucci
Keyword(s):  
Particle Size ◽  
Water Supply ◽  
Risk Reduction ◽  
Settling Velocity ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Particle Size Fractions ◽  
Size Classes ◽  
Large Particles ◽  
Water Supply Reservoirs

Artificial cow pats were seeded with Cryptosporidium oocysts and subjected to a simulated rainfall event. The runoff from the faecal pat was collected and different particle size fractions were collected within settling columns by exploiting the size-dependent settling velocities. Particle size and Cryptosporidium concentration distribution at 10 cm below the surface was measured at regular intervals over 24 h. Initially a large proportion of the total volume of particles belonged to the larger size classes (>17 μm). However, throughout the course of the experiment, there was a sequential loss of the larger size classes from the sampling depth and a predominance of smaller particles (<17 μm). The Cryptosporidium concentration at 10 cm depth did not change throughout the experiment. In the second experiment samples were taken from different depths within the settling column. Initially 26% of particles were in the size range 124–492 μm. However, as these large particles settled there was an enrichment at 30 cm after one hour (36.5–49.3%). There was a concomitant enrichment of smaller particles near the surface after 1 h and 24 h. For Pat 1 there was no difference in Cryptosporidium concentration with depth after 1 h and 24 h. In Pat 2 there was a difference in concentration between the surface and 30 cm after 24 h. However, this could be explained by the settling velocity of a single oocyst. The results suggested that oocysts are not associated with large particles, but exist in faecal runoff as single oocysts and hence have a low (0.1 m d−1) settling velocity. The implications of this low settling velocity on Cryptosporidium risk reduction within water supply reservoirs was investigated through the application of a three-dimensional model of oocyst fate and transport to a moderately sized reservoir (26 GL). The model indicated that the role of settling on oocyst concentration reduction within the water column is between one and three orders of magnitude less than that caused by advection and dilution, depending on the strength of hydrodynamic forcing.

scholarly journals Hydrological Restoration and Water Resource Management of Siberian Crane (Grus leucogeranus) Stopover Wetlands

Water ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1714 ◽  
Author(s):  
Haibo Jiang ◽  
Chunguang He ◽  
Wenbo Luo ◽  
Haijun Yang ◽  
Lianxi Sheng ◽  
...  
Keyword(s):  
Resource Management ◽  
Water Supply ◽  
Water Resource ◽  
Water Demand ◽  
Water Resource Management ◽  
Three Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Siberian Crane ◽  
Ecological Water Demand

Habitat loss is a key factor affecting Siberian crane stopovers. The accurate calculation of water supply and effective water resource management schemes plays an important role in stopover habitat restoration for the Siberian crane. In this paper, the ecological water demand was calculated and corrected by developing a three-dimensional model. The results indicated that the calculated minimum and optimum ecological water demand values for the Siberian crane were 2.47 × 108 m3~3.66 × 108 m3 and 4.96 × 108 m3~10.36 × 108 m3, respectively, in the study area. After correction with the three-dimensional model, the minimum and optimum ecological water demand values were 3.75 × 108 m3 and 5.21 × 108 m3, respectively. A water resource management scheme was established to restore Siberian crane habitat. Continuous, area-specific and simulated flood water supply options based on water diversions were used to supply water. The autumn is the best season for area-specific and simulating flood water supply. These results can serve as a reference for protecting other waterbirds and restoring wetlands in semi-arid areas.

A combined experimental and numerical approach to the assessment of floc settling velocity using fractal geometry

2020 ◽  
Vol 81 (5) ◽  
pp. 915-924 ◽  
Author(s):  
R. B. Moruzzi ◽  
J. Bridgeman ◽  
P. A. G. Silva
Keyword(s):  
Particle Size ◽  
Fractal Dimension ◽  
Primary Particle ◽  
Settling Velocity ◽  
Three Dimensional ◽  
Fractal Dimensions ◽  
Numerical Approach ◽  
Primary Particle Size ◽  
Fractal Aggregates ◽  
Water And Wastewater Treatment

Abstract Sedimentation processes are fundamental to solids/liquid separation in water and wastewater treatment, and therefore a robust understanding of the settlement characteristics of mass fractal aggregates (flocs) formed in the flocculation stage is fundamental to optimized settlement tank design and operation. However, the use of settling as a technique to determine aggregates' traits is limited by current understanding of permeability. In this paper, we combine experimental and numerical approaches to assess settling velocities of fractal aggregates. Using a non-intrusive in situ digital image-based method, three- and two-dimensional fractal dimensions were calculated for kaolin-based flocs. By considering shape and fractal dimension, the porosity, density and settling velocities of the flocs were calculated individually, and settling velocities compared with those of spheres of the same density using Stokes' law. Shape analysis shows that the settling velocities for fractal aggregates may be greater or less than those for perfect spheres. For example, fractal aggregates with floc fractal dimension, Df = 2.61, floc size, df > 320 μm and dp = 7.5 μm settle with lower velocities than those predicted by Stokes' law; whilst, for Df = 2.33, all aggregates of df > 70 μm and dp = 7.5 μm settled below the velocity calculated by Stokes' law for spheres. Conversely, fractal settling velocities were higher than spheres for all the range of sizes, when Df of 2.83 was simulated. The ratio of fractal aggregate to sphere settling velocity (the former being obtained from fractal porosity and density considerations), varied from 0.16 to 4.11 for aggregates in the range of 10 and 1,000 μm, primary particle size of 7.5 μm and a three-dimensional fractal dimension between 2.33 and 2.83. However, the ratio decreases to the range of 0.04–2.92 when primary particle size changes to 1.0 μm for the same fractal dimensions. Using the floc analysis technique developed here, the results demonstrate the difference in settlement behaviour between the approach developed here and the traditional Stokes' law approach using solid spheres. The technique and results demonstrate the improvements in understanding, and hence value to be derived, from an analysis based on fractal, rather than Euclidean, geometry when considering flocculation and subsequent clarification performance.

Three-dimensional model for particle-size segregation by shaking

1992 ◽  
Vol 69 (4) ◽  
pp. 640-643 ◽  
Author(s):  
Rémi Jullien ◽  
Paul Meakin ◽  
André Pavlovitch
Keyword(s):  
Particle Size ◽  
Three Dimensional ◽  
Dimensional Model ◽  
Size Segregation ◽  
Three Dimensional Model

scholarly journals Three-Dimensional Modeling of Green Sand and Squeeze Molding Simulation

2018 ◽  
Vol 925 ◽  
pp. 473-480 ◽  
Author(s):  
Yuuka Ito ◽  
Yasuhiro Maeda
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Three Dimensional ◽  
Hard Core ◽  
Sand Mold ◽  
Particle Model ◽  
Three Dimensional Model ◽  
Green Sand ◽  
Squeeze Pressure

The green sand mold with good mold properties are useful to obtain the sound cast iron castings. For example, the green sand mold with high density and uniform for compacting characteristics would be required. Molding simulation is indispensable to make a good sand mold. In recent years, the package software was released from software vendors of foundry CAE, and the demand for molding simulation is increasing. Fundamental algorithms of the green sand particulate model and the three-dimensional Discrete Element Method (DEM) were proposed. They take into consideration of the particle size distribution and the cohesion of green sand particles.In this study, the squeeze molding simulation is carried out and we execute the re-development of this method under the current computer environment. They are tried to simulate the dynamic behavior during molding and to predict the mold properties after squeeze molding. The characteristics of green sand with cohesion are reflected in the particle model called Hard-Core/Soft-Shell. The compacting behavior of squeeze molding is traced numerically, and the visualization by a three-dimensional model and comparison of dynamics molding are carried out. From the simulation with several kinds of particle distribution, it becomes clear the relationship between the void fraction and the squeeze pressure during molding. The effect of particle size distribution on sand compacting behavior is also clarified. Furthermore, the three-dimensional display of green sand with particle size distribution is very effective in the post-processing.

scholarly journals Measurement of snow particle size and velocity in avalanche powder clouds

2017 ◽  
Vol 63 (238) ◽  
pp. 249-257 ◽  
Author(s):  
YOICHI ITO ◽  
FLORENCE NAAIM-BOUVET ◽  
KOUICHI NISHIMURA ◽  
HERVÉ BELLOT ◽  
EMMANUEL THIBERT ◽  
...  
Keyword(s):  
Particle Size ◽  
Settling Velocity ◽  
Test Site ◽  
The Core ◽  
Large Particles ◽  
Ultrasonic Anemometer ◽  
Particle Speed ◽  
Avalanche Flow ◽  
Surface Particle ◽  
Snow Particle

ABSTRACTParticle size, particle speed and airflow speed have been measured in the powder snow clouds of avalanches to investigate the suspension and transportation processes of snow particles. The avalanches were artificially triggered at the Lautaret full-scale avalanche test-site (French Alps) where an ultrasonic anemometer and a snow particle counter were setup in an avalanche track for measurements. Relatively large particles were observed during passage of the avalanche head and then the size of the particles slightly decreased as the core of the avalanche passed the measurement station. The particle size distribution was well fitted by a gamma distribution function. A condition for suspension of particles within the cloud based on the ratio of vertical velocity fluctuation to particle settling velocity suggests that the large particles near the avalanche head are not lifted up by turbulent diffusion, but rather ejected by a process involving collisions between the avalanche flow and the rough snow surface. Particle speeds were lower than the airflow speed when large particles were present in the powder cloud.

Three-Dimensional Model for Virtual Surgical Simulation, during Complex Skull Base Surgery and Aneurysm Surgery

Skull Base ◽  
2008 ◽  
Vol 18 (S 01) ◽  
Author(s):  
Akio Morita ◽  
Toshikazu Kimura ◽  
Shigeo Sora ◽  
Kengo Nishimura ◽  
Hisayuki Sugiyama ◽  
...  
Keyword(s):  
Skull Base ◽  
Surgical Simulation ◽  
Skull Base Surgery ◽  
Three Dimensional ◽  
Aneurysm Surgery ◽  
Dimensional Model ◽  
Three Dimensional Model
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