Structural controls on floc strength and transport

2004 ◽  
Vol 31 (4) ◽  
pp. 569-578 ◽  
Author(s):  
Ian G Droppo
Keyword(s):  
Extracellular Polymeric Substances ◽  
Correlative Microscopy ◽  
Floc Size ◽  
Biochemical Processes ◽  
Structural Controls ◽  
Floc Structure ◽  
Physical Chemical ◽  
Combined Sewer ◽  
Size Stability ◽  
Floc Strength

An examination of how floc structure (internal and external) influences floc strength and transport is described. Samples were collected from both a natural river and a combined sewer outfall to provide significantly different structures for comparison. Regardless of floc type, the internal matrix was observed to be mediated by a dynamic microbial community. Microbial secretions of fibrilar extracellular polymeric substances (EPS) were found to be interwoven within the floc forming a framework and providing structural stability. This continually changing framework (due to floc physical, chemical, and biological activity) is shown to have extending influence over floc transport by modifying floc size, stability, density, porosity, and biochemical processes. This paper uses correlative microscopy to assess floc structure and behaviour in terms of the transport of sediments and associated contaminants. A conceptual model is provided which links floc strength to sediment transport (deposition and erosion) in the water column and at the sediment water interface.Key words: flocculation, bacteria, extracellular polymeric substances, stability, transport, structure.

Characterising natural organic matter flocs

2004 ◽  
Vol 4 (4) ◽  
pp. 79-87 ◽  
Author(s):  
P. Jarvis ◽  
B. Jefferson ◽  
S.A. Parsons
Keyword(s):  
Organic Matter ◽  
Natural Organic Matter ◽  
Structural Characteristics ◽  
Floc Size ◽  
Water Characteristics ◽  
Floc Structure ◽  
Floc Characteristics ◽  
Floc Strength ◽  
Settling Column ◽  
One Year

Using a dynamic optical technique and settling column apparatus, natural organic matter floc structural characteristics were monitored and evaluated over a one year period to monitor the seasonal variation in floc structure at optimum coagulation dose and pH. The results show that flocs changed seasonally with different growth rates, size, response to shear and settling rate. Autumn and summer flocs were shown to be larger and less resistant to floc breakage when compared to the other seasons, suggesting reduced floc strength. Floc strength was observed to increase with smaller median floc size. The results of the settling tests indicated that the autumnal flocs were of a more open structure which helped to explain why they settled faster. In summary, the autumnal flocs had significantly different floc characteristics although it was difficult to relate the floc structure with the incoming water characteristics.

Use of Wood Biomass in Slovakia

2014 ◽  
Vol 1001 ◽  
pp. 126-130
Author(s):  
Tomáš Bakalár ◽  
Henrieta Pavolová ◽  
Milan Búgel ◽  
Ľubica Kozáková
Keyword(s):  
Energy Source ◽  
Renewable Energy Source ◽  
Renewable Energy ◽  
Organic Material ◽  
Chemical Processes ◽  
Wood Chips ◽  
Wood Biomass ◽  
Biochemical Processes ◽  
Physical Chemical ◽  
Thermochemical Processes

Biomass is organic material, the second most important source of energy. Biomass is a renewable energy source. Wood biomass is used as source of energy for heating in many regions in Slovakia. It is because of its availability. Wood biomass is an easily accessible and affordable source of energy. At present, thermochemical processes, biochemical processes and physical-chemical processes are used for biomass utilization. In the article a suitable technology for combustion of wood chips is proposed. It consists of five main technological parts: transport of wood chips, silo, combustion boiler, and stack.

Effect of phosphorus limitation on microbial floc structure and gene expression in activated sludge

2006 ◽  
Vol 54 (1) ◽  
pp. 247-255 ◽  
Author(s):  
J.R. Liu ◽  
C.T. Liu ◽  
E.A. Edwards ◽  
S.N. Liss
Keyword(s):  
Gene Expression ◽  
Activated Sludge ◽  
Extracellular Polymeric Substances ◽  
Morphological Changes ◽  
Cell Structure ◽  
Operating Conditions ◽  
P Limitation ◽  
Floc Structure ◽  
The Impact ◽  
Log Ratio

The effect of limiting phosphorus (P) in activated sludge was investigated in laboratory-scale sequencing batch reactors (SBRs). Correlative microscopy revealed that P-limitation (COD:N:P=100:5:0.05) leads to morphological changes in floc structure and the composition of extracellular polymeric substances (EPS). This was found to be accompanied by expression of quorum-sensing in an acyl homoserine lactone bioassay. Differential gene expression in relation to P-limitation was examined in a global profile using the Affymetrix™ Escherichia coli antisense genomic microarray. Three separate experiments were conducted where the impact of P-limitation was examined under batch conditions and in SBRs at stable operating conditions and within 3–7 days following a down-shift in P. Significant changes in open reading frames (ORF) and intergenic regions based on the E. coli microarray were observed. Several genes associated with cell structure, including slt, wbbH, fimH, amB, rfaJ and slp were found to be expressed. Quorum regulated genes were also found to be expressed including psiF which is known to be induced by P-starvation (92% confidence level; 1.45 log ratio).

scholarly journals Bread production technology modelling using hop starter in ovens of various types

2020 ◽  
pp. 22-31
Author(s):  
V. A. Bukhovets ◽  
T. V. Kirillova ◽  
N. A. Fokina ◽  
I. V. Romanov
Keyword(s):  
Regression Models ◽  
Optimization Problem ◽  
Binary Variable ◽  
Biochemical Processes ◽  
Physical Chemical ◽  
Optimal Values ◽  
Bread Production ◽  
Heat And Moisture ◽  
Multicriteria Optimization Problem ◽  
Required Quality

The article studies the processes of structure formation of baked dough pieces using wheat and hop starters and changes in the properties of finished products and semi-finished products depending on the baking methods. A whole complex of physical, chemical and biochemical processes takes place in the dough piece during baking under the influence of heat and moisture, which causes considerable changes in the bread dough. These processes cause changes in the baked dough piece, that cause turning the dough into bread. Duration and intensity of the processes occurring on the surface and in the inner layers of the dough piece during baking depend on the temperature. Therefore, creation of optimal modes of heating the baked dough piece at various stages allows you to get products of the required quality. To simulate the processes of crumb formation, changes in temperature inside the dough piece of baking, and specific volume over time with different methods of dough and baking, regression models were used, that take into account the influence of qualitative factors. Each qualitative factor having two grades was replaced by one binary variable. The solution of a multicriteria optimization problem showed that the studied indicators reach the optimal values when baking in an air-o-steam and preparing a dough using hop starter.

scholarly journals Shear-Dependent Yield Stress of Iron Ore Fine Tailings in Two-Step Flocculation Process

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Ying Yang ◽  
Hongjiang Wang ◽  
Bern Klein ◽  
Aixiang Wu
Keyword(s):  
Fractal Dimension ◽  
Yield Stress ◽  
Network Structure ◽  
Iron Ore ◽  
Shear Resistance ◽  
Strength Factor ◽  
Floc Size ◽  
Fine Tailings ◽  
Floc Strength ◽  
Flocculation Process

Both shear and flocculation have a significant influence on the rheological behavior of tailings, especially the yield stress. In the two-step flocculation process, the above two kinds of actions exist at the same time, and they influence each other. In order to explore the change rule of the yield stress and its internal causes, a two-step flocculation process of the iron ore fine tailings with different shear conditions in the four different phases was designed. In the primary flocculation phase, tailing particles combined with the primary flocculant and formed a primary floc network structure. In the primary broken phase, shear destroyed the primary floc network structure and decreased the average floc size, so the shear-dependent yield stress, the floc strength factor, and the fractal dimension decreased. In the secondary flocculation phase, broken floc combined with the secondary flocculant and produced a more compact floc network structure which had a better shear resistance. Therefore, in the secondary broken phase, with the increase of shear, the decrease of yield stress, the floc strength factor, and fractal dimension were less obvious than that in the primary broken phase. In both two broken phases, the yield stress of the secondary flocculating slurry was always higher than that of the primary flocculating slurry, but with the increase of shear, the difference became smaller. The floc strength and fractal dimension also showed the same rule. The internal reasons for the stronger shear resistance of the secondary flocculating slurry were the increase of the number of binding sites, the electric neutralization between the two flocculants, and the steric hindrance effect of the flocculants.

scholarly journals Characterisation of floc size, effective density and sedimentation under various flocculation mechanisms

2020 ◽  
Vol 82 (7) ◽  
pp. 1261-1271
Author(s):  
Yuping Fan ◽  
Xiaomin Ma ◽  
Xianshu Dong ◽  
Zeyu Feng ◽  
Yingdi Dong
Keyword(s):  
Settling Velocity ◽  
Structural Characteristics ◽  
Effective Density ◽  
Floc Size ◽  
Floc Structure ◽  
Trivalent Cations ◽  
Coal Tailings ◽  
Better Than ◽  
Flocculation Mechanisms

Abstract Floc structure plays an important role in the separation of coal wastewater. In this study, a camera-based method is used to evaluate quantitatively the structural characteristics of flocs generated by different coagulants and flocculants. The correlations between particle size, settlement velocity and effective density of coal tailings flocs are analysed. The results show that the statistical settling velocity increases linearly with floc size, while the effective density decreases with increase in floc size. Different flocculation mechanisms lead to diverse growth abilities of flocs. When the flocculant is used alone, the quality of the flocs generated by the flocculants, cationic polyacrylamide (CPAM) and non-ionic polyacrylamide (NPAM), is better than that generated by anionic polyacrylamide (APAM). However, the combination of trivalent cations and APAM yields a much better effect than that obtained using CPAM and NPAM. Flocs become larger and more compact when treated with a coagulant combined with a flocculant.

Microbial floc stabilization and preparation for structural analysis by correlative microscopy

1996 ◽  
Vol 34 (5-6) ◽  
pp. 155-162 ◽  
Author(s):  
Ian G. Droppo ◽  
Derrick T. Flannigan ◽  
Gary G. Leppard ◽  
Steven N. Liss
Keyword(s):  
Three Dimensional ◽  
Microscopic Analysis ◽  
Confocal Laser ◽  
Natural State ◽  
Correlative Microscopy ◽  
Floc Size ◽  
Microbial Flocs ◽  
Multiple Sampling ◽  
Transmission Electron ◽  
The Matrix

In the analysis of microbial flocs from activated sludge it is important to stabilize these structures and their components for structural studies sufficiently to assess, minimize and conceptually balance artifacts, particularly during manipulation. By employing multi-technique stabilization and immediate preservation it is possible to analyze a single sample by correlative microscopy (conventional optical microscopy (COM), scanning confocal laser microscopy (SCLM), and transmission electron microscopy (TEM)). This approach minimizes variability associated with multiple sampling. Floc samples were collected using plankton chambers consisting of reservoirs with a removable circular microscope slide. Flocs which come to rest on the slide are stabilized within low melting point agarose. The solidified gel is a clear, highly porous and resilient medium amenable to further staining, washing, sub-sampling or direct microscopic analysis. Stabilization in agarose was found not to significantly influence floc size distribution. The use of agarose was found to be compatible with SCLM and TEM techniques and minimized perturbations. Agar-embedded samples were easily infused with Nanoplast, a hydrophilic melamine resin, which stabilizes material in its natural state. This facilitates the ultrastructural analysis of the three-dimensional fibrillar architecture of the floc matrix. The matrix is found to consist of complex pores bounded by fibrils of 4-6 nm diameter.

Evaluation of floc strength by morphological analysis and PDA online monitoring

2007 ◽  
Vol 56 (10) ◽  
pp. 117-124 ◽  
Author(s):  
Pengkang K. Jin ◽  
Xiaochang C. Wang ◽  
Haixia Chai
Keyword(s):  
Morphological Analysis ◽  
Online Monitoring ◽  
Particle Dispersion ◽  
Force Coefficient ◽  
Floc Size ◽  
Binding Force ◽  
Jar Test ◽  
Floc Strength ◽  
Series Of Experiments ◽  
Flocculated Suspension

This paper established a method for the evaluation of floc strength by morphological analysis and PDA online monitoring. Theoretically, the binding force of a floc can be expressed as B=k1d2Df/3, where k1 is a coefficient, d is floc size and Df is the fractal dimension of the floc. In order to calculate the binding force under a given flocculation condition, a jar test was conducted and d and Df were measured by image analysis. A shear force was exerted on the grown flocs by introducing the flocculated suspension through a transparent tube where the velocity gradient value of the flow could be accurately controlled. As the tube was connected with a particle dispersion analyzer (PDA), the condition of floc breakage was online monitored and the critical condition was identified by analyzing the PDA outputs (FI curves). The binding force coefficient k1 could thus be determined, and the binding force B which represented the floc strength was evaluated. The validity of this method was proved by a series of experiments using aluminium sulphate as coagulant for the flocculation of humic substances.

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