Kinetic analysis of PAC cake-layer formation in hybrid PAC-MF systems

2008 ◽  
Vol 8 (1) ◽  
pp. 1-7 ◽  
Author(s):  
S. Takizawa ◽  
P. Zhao ◽  
S. Ohgaki ◽  
H. Katayama
Keyword(s):  
Membrane Filtration ◽  
Specific Resistance ◽  
Experimental Studies ◽  
Ceramic Membranes ◽  
Layer Formation ◽  
Void Space ◽  
Filtration Resistance ◽  
Saw Dust ◽  
Cake Layer ◽  
The Difference

Experimental studies were conducted to evaluate the effectiveness of backwashing and air-scouring to prevent cake-layer formation on the membranes in a hybrid PAC-MF process. The membrane filtration chamber used in this study was separated into two zones; namely, the PAC adsorption zone (PAZ) and the membrane filtration zone (MFZ). In MFZ tubular ceramic membranes were installed, and powdered activated carbon (PAC) was suspended in PAZ at a concentration of 20 g/L by aeration. Air-scouring and backwashing rates were gradually increased to see if these physical cleaning measures can reduce or maintain the filtration resistance due to formation of PAC cake layer on the membrane. Two types of saw-dust PAC having different sizes were used to find the difference of the effects of air-scouring and backwashing. A smaller PAC (Shirasagi C1, Japan EnviroChemicals, Co.) showed a slower increasing rate of filtration resistance than the larger PAC (Shirasagi S-10, Japan EnviroChemicals, Co.). It was found that air-scouring didn't reduce the rate of cake fouling formation of PAC S-10, but can quite effectively reduce the rate of PAC C-1 attachment to the membrane. On the contrary, backwashing was not effective for PAC C-1, but quite effective for PAC S-10. PAC C1 formed a porous cake with low specific resistance, which can be easily removed by air-scouring, but cannot be removed by backwashing. On the other hand, PAC S-10 formed a tight cake layer because suspended particles get in to the void space between the PAC S-10. A dynamic model was proposed to explain the effect of air-scouring and backwashing to removal cake layer from the membranes.

scholarly journals Membrane Fouling Mechanisms in Combined Microfiltration-Coagulation of Algal Rich Water Applying Ceramic Membranes

Membranes ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 33 ◽  
Author(s):  
Kitae Park ◽  
Pooreum Kim ◽  
Hyoung Gun Kim ◽  
JiHoon Kim
Keyword(s):  
Membrane Fouling ◽  
Ceramic Membrane ◽  
Ceramic Membranes ◽  
Constant Flow ◽  
Filtration Resistance ◽  
Fouling Mechanism ◽  
Coagulant Dosage ◽  
Cake Layer ◽  
Specific Cake Resistance ◽  
Resistance Value

In this paper, we investigated the membrane fouling mechanism according to the coagulant dosage in algal rich water using a ceramic membrane. The algae that were used in this experiment were Microcystis sp. of cyanobacteria, and the fouling mechanism was analyzed through irrigation and filtration resistance through a constant flow operation. The experimental results showed that the filtration resistance decreased as the coagulant dosage increased, but the irreversibility at above optimum coagulant dosage increased. Additionally, as the coagulant dosage increased, the resistance value due to cake and adsorption contamination decreased, and membrane fouling by adsorption was dominant in comparison with cake fouling and adsorption fouling. The specific cake resistance was decreased as the coagulant dosage increased. The characteristics of the cake layer according to the coagulant dosage were found to loosely form the cake layer by increasing micro-size algae as the coagulant dosage increased. The results of this experiment confirmed the membrane fouling mechanism according to coagulant dosage when the ceramic membrane filtered algal rich water.

Modeling of pore blocking and cake layer formation in membrane filtration for wastewater treatment

Desalination ◽  
2006 ◽  
Vol 189 (1-3) ◽  
pp. 97-109 ◽  
Author(s):  
A. Broeckmann ◽  
J. Busch ◽  
T. Wintgens ◽  
W. Marquardt
Keyword(s):  
Wastewater Treatment ◽  
Membrane Filtration ◽  
Layer Formation ◽  
Pore Blocking ◽  
Cake Layer

Behavior of micro-particles in monolith ceramic membrane filtration with pre-coagulation

2004 ◽  
Vol 50 (12) ◽  
pp. 317-325 ◽  
Author(s):  
H. Yonekawa ◽  
Y. Tomita ◽  
Y. Watanabe
Keyword(s):  
Membrane Filtration ◽  
Ceramic Membrane ◽  
Membrane Surface ◽  
Flow Analysis ◽  
Ceramic Membranes ◽  
End Point ◽  
Micro Particles ◽  
Dead End ◽  
Cake Layer ◽  
The Dead

This paper is intended to clarify the characteristics unique to monolith ceramic membranes with pre-coagulation by referring to the behavior of micro-particles. Flow analysis and experiments have proved that monolith ceramic membranes show a unique flow pattern in the channels within the element, causing extremely rapid flocculation in the channel during dead-end filtration. It was assumed that charge-neutralized micro-particles concentrated near the membrane surface grow in size due to flocculation, and as a result, coarse micro-particles were taken up by the shearing force to flow out. As the dead end points of flow in all the channels are located near the end of the channels with higher filterability, most of the flocculated coarse particles are formed to a columnar cake intensively at the dead end point. Therefore cake layer forming on the membrane other than around the dead end point is alleviated. This behavior of particle flocculation and cake formation at the dead end point within the channels are unique characteristics of monolith ceramic membranes. This is why all monolith ceramic membrane water purification systems operating in Japan do not have pretreatment equipment for flocculation and sedimentation.

Cross-flow ultrafiltration for surface water treatment in North Thailand

2000 ◽  
Vol 41 (10-11) ◽  
pp. 69-76
Author(s):  
S. Takizawa ◽  
S. Babel ◽  
N. Pradhan ◽  
T. Prathomrungsiyunkul ◽  
K. Suwannarit ◽  
...  
Keyword(s):  
Surface Water ◽  
Membrane Fouling ◽  
Experimental Studies ◽  
Cross Flow ◽  
Variable Cross ◽  
Chemical Cleaning ◽  
Filtration Resistance ◽  
Cake Layer ◽  
The Cross ◽  
North Thailand

Experimental studies on cross-flow ultrafiltration were carried out to evaluate the applicability to treat surface water in North Thailand. Hollow-fiber UF modules (polyacrylonitrile, MWCO 13,000 daltons, I.D. 0.8 mm, and module length 1126 mm) were used in the experiments. While the permeation flux was controlled at 1.0 m/d, the cross-flow velocity was either fixed at 0.1 m/s or varied as the membrane fouling proceeded. The comparative study on fixed and variable cross-flow velocities revealed that the variable velocity operation was superior to achieve a longer operational period before chemical cleaning. Intensive backwashing was performed when the filtration resistance rose over 1013 m–1, which revealed that more than 80% of the resistance was caused by cake-layer that can be removed by the intensive backwashing. However, the operational period was only 54% of the one for the new membranes, which suggested that the percentage reduction of the filtration resistance should not be used as an index of the efficiency of chemical or physical membrane cleaning. Despite shortened operational periods, the intensive backwashing was proposed to be an easy and rapid method to recover the permeability of fouled membranes without chemical use. The cross-flow UF system used in this study was found to be easy to operate even in small water systems in developing countries.

Filtration resistance induced by ammonia oxidizers accumulating on the rotating membrane disk

1998 ◽  
Vol 38 (4-5) ◽  
pp. 443-452
Author(s):  
Katsuki Kimura ◽  
Yoshimasa Watanabe ◽  
Naoki Ohkuma
Keyword(s):  
Membrane Filtration ◽  
Extracellular Polymeric Substances ◽  
Drinking Water Treatment ◽  
Treatment Method ◽  
Operating Conditions ◽  
Transmembrane Pressure ◽  
Ammonia Oxidizers ◽  
Filtration Resistance ◽  
Rotating Membrane Disk ◽  
Membrane Disk

Membrane filtration and oxidation of ammonia were simultaneously performed by using a rotating membrane disk module. Nitrification performance, composition of the accumulated cakes on the membrane and the filtration resistances were investigated under five different operating conditions. The filtration resistance due to the accumulated cake on the membrane was found to be dominant in this treatment method, compared to the resistance due to the micropore plugging or irreversible adherence. The cake consisted mainly of iron, humic substances and bacteria. The possibility that extracellular polymeric substances were related to the cake resistance was also shown. The composition of the cake depended on the length and the condition of operation. Accumulation of ammonia oxidizers caused by oxidation of low concentrations of ammonia (less than 1 mg/l) did not increase transmembrane pressure significantly. Therefore, the application of this treatment method for drinking water treatment is feasible. Filtration resistance due to the micropore plugging or irreversible adherence to the membrane was caused by organic substances.

scholarly journals Variety resistance of winter barley to powdery mildew in the field in 1976−2005

2008 ◽  
Vol 43 (No. 3) ◽  
pp. 87-96 ◽  
Author(s):  
A. Dreiseitl
Keyword(s):  
Powdery Mildew ◽  
Disease Severity ◽  
Powdery Mildew Resistance ◽  
Specific Resistance ◽  
Winter Barley ◽  
Mildew Resistance ◽  
Average Resistance ◽  
The Difference ◽  
The Given ◽  
Resistance Of Varieties

The results of evaluation of powdery mildew resistance in winter barley varieties in 285 Czech Official Trials conducted at 20 locations were analysed. Over the period, the number of varieties tested per year increased from four to seven in 1976−1985 to 53−61 in 2002−2005. To assess the resistance of varieties, only trials with sufficient disease severity were used. In 1976−2000, six varieties (1.7% of the varieties tested in the given years) ranked among resistant (average resistance of a variety in a year > 7.5) including NR-468 possessing the gene <i>Mla13</i>, KM-2099 with <i>mlo</i> and Marinka with the genes <i>Mla7</i>, <i>MlaMu2</i>. In 2001−2005, already 33 varieties (16.9%) ranked among resistant, of which Traminer possessing the genes <i>Ml(St)</i> and <i>Ml(IM9 </i> dominated. The proportion of susceptible varieties (average resistance ≤ 5.5) did not change in the two mentioned periods. Two-rowed varieties began to be tested as late as in 1990 (the first variety was Danilo), however, no difference was found in the resistance of two- and six-rowed varieties. Using an example of two pairs of varieties (Dura-Miraj and Marinka-Tiffany) with identical genes for specific resistance but with different resistance in the field, the efficiency of non-specific resistance is discussed. The resistance of domestic and foreign varieties was similar in 1994−2000; however, in 2001−2005 the difference was 0.75 point to disadvantage of domestic ones.

scholarly journals Potential Pitfalls in Membrane Fouling Evaluation: Merits of Data Representation as Resistance Instead of Flux Decline in Membrane Filtration

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 460
Author(s):  
Bastiaan Blankert ◽  
Bart Van der Bruggen ◽  
Amy E. Childress ◽  
Noreddine Ghaffour ◽  
Johannes S. Vrouwenvelder
Keyword(s):  
Membrane Fouling ◽  
Membrane Filtration ◽  
Data Representation ◽  
Strong Impact ◽  
Experimental Conditions ◽  
Permeable Membrane ◽  
Dead End ◽  
Flux Decline ◽  
The Difference ◽  
Filtration Flux

The manner in which membrane-fouling experiments are conducted and how fouling performance data are represented have a strong impact on both how the data are interpreted and on the conclusions that may be drawn. We provide a couple of examples to prove that it is possible to obtain misleading conclusions from commonly used representations of fouling data. Although the illustrative example revolves around dead-end ultrafiltration, the underlying principles are applicable to a wider range of membrane processes. When choosing the experimental conditions and how to represent fouling data, there are three main factors that should be considered: (I) the foulant mass is principally related to the filtered volume; (II) the filtration flux can exacerbate fouling effects (e.g., concentration polarization and cake compression); and (III) the practice of normalization, as in dividing by an initial value, disregards the difference in driving force and divides the fouling effect by different numbers. Thus, a bias may occur that favors the experimental condition with the lower filtration flux and the less-permeable membrane. It is recommended to: (I) avoid relative fouling performance indicators, such as relative flux decline (J/J0); (II) use resistance vs. specific volume; and (III) use flux-controlled experiments for fouling performance evaluation.

Investigation of Regression-Based Effect Size Methods Developed in Single-Subject Studies

2021 ◽  
pp. 014544552110540
Author(s):  
Nihal Sen
Keyword(s):  
Effect Size ◽  
Experimental Studies ◽  
Single Subject ◽  
Single Subject Design ◽  
Data Set ◽  
Design Studies ◽  
Sample Data ◽  
The Difference ◽  
D Values ◽  
Effect Size Calculation

The purpose of this study is to provide a brief introduction to effect size calculation in single-subject design studies, including a description of nonparametric and regression-based effect sizes. We then focus the rest of the tutorial on common regression-based methods used to calculate effect size in single-subject experimental studies. We start by first describing the difference between five regression-based methods (Gorsuch, White et al., Center et al., Allison and Gorman, Huitema and McKean). This is followed by an example using the five regression-based effect size methods and a demonstration how these methods can be applied using a sample data set. In this way, the question of how the values obtained from different effect size methods differ was answered. The specific regression models used in these five regression-based methods and how these models can be obtained from the SPSS program were shown. R2 values obtained from these five methods were converted to Cohen’s d value and compared in this study. The d values obtained from the same data set were estimated as 0.003, 0.357, 2.180, 3.470, and 2.108 for the Allison and Gorman, Gorsuch, White et al., Center et al., as well as for Huitema and McKean methods, respectively. A brief description of selected statistical programs available to conduct regression-based methods was given.

scholarly journals Design And Experimental Studies Of Flexible Trailing Edge For Variable Camber Morphing Wing

2021 ◽  
Author(s):  
Ahmad T. Kalaji
Keyword(s):  
Experimental Data ◽  
Carbon Fiber ◽  
Deflection Angle ◽  
Experimental Studies ◽  
Morphing Wing ◽  
Trailing Edge ◽  
Wing Section ◽  
Rigid Constraint ◽  
The Difference

This thesis presents a flexible trailing edge mechanism capable of undergoing a change in camber for a wing section. The mechanism takes advantage of a rigid constraint between the ends of two flexible carbon fiber panels, which produces a deflection when there is a difference in length between the two panels. A prototype was designed and built and experimental data was collected for the deformation of the panels for different values of lengths and analyzed to find a function to describe the coefficients which form the polynomials describing the shape for each of the panels, based on the difference in length value. Deflection and deflection angle results were used to develop a controller which will calculate the required change in length based on a deflection or angle and a bottom panel length input.

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