The Relationship between Critical Flux and Membrane Fouling

2014 ◽  
Vol 535 ◽  
pp. 675-678
Author(s):  
Wei Ying Li ◽  
Jun Peng Zhang ◽  
Wen Ming Li
Keyword(s):  
Membrane Fouling ◽  
Sand Filtration ◽  
Short Term ◽  
Step Method ◽  
Critical Flux ◽  
Surface Features ◽  
On Line ◽  
The Relationship

The critical flux was chosen to show surface features of the membrane fouling and it was determined by the flux-step method. The critical flux of on-line coagulation-UF, sedimentation-UF and sand filtration-UF was investigated and its value was 86.5 L/m2h80.5L/m2h and 68.1L/m2h, respectively. At the same time, the increasing rate of TMP were always lower than the corresponding values measured for the short-term flux-step experiments.

scholarly journals Creating Relationships Using On-Line Dating Services: A Preliminary Mapping of French People’s Views

2019 ◽  
Vol 18 (1) ◽  
pp. 1-6
Author(s):  
Mélanie Gauché ◽  
Lucie Brard
Keyword(s):  
Romantic Relationships ◽  
Online Dating ◽  
Short Term ◽  
Emotional Involvement ◽  
Five Factors ◽  
On Line ◽  
Scenario Technique ◽  
The Relationship ◽  
Affective Involvement

We explored people’s views regarding the kind of relationship that can be expected and created using such websites. In the current study, we used the same scenario technique. Vignettes depicting the kind of relationship an individual expected to find through the use of an online dating service were created by orthogonal combination of five factors: (a) passion; that is, the level of personal, affective involvement in the relationship, (b) intimacy; that is, the type of relationship desired (friendship vs. intimate/sexual), (c) commitment; that is, the expected duration of the relationship (short term vs. long term), (d) the user’s gender, and (e) the user’s age. Three contrasted positions were found. A minority of participants considered that creating a relationship using dating services was never very easy. A plurality of participants considered that creating either long-term romantic relationships or short-term, more “utilitarian” relationships was considerably easier than creating either short-term romantic relationships or long-term, more “utilitarian” relationships. Another plurality of participants considered that creating any relationship was quite possible. These participants disconnected the commonly admitted association between the duration of a relationship and level of emotional involvement. In other words, they considered that creating a passionate but short-lived relationship was not more difficult than creating any other kind of relationships.

Monitoring of transparent exopolymer particles (TEP) in a membrane bioreactor (MBR) and correlation with other fouling indicators

2008 ◽  
Vol 58 (10) ◽  
pp. 1903-1909 ◽  
Author(s):  
T. de la Torre ◽  
B. Lesjean ◽  
A. Drews ◽  
M. Kraume
Keyword(s):  
Linear Correlation ◽  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Membrane Systems ◽  
Transparent Exopolymer Particles ◽  
Critical Flux ◽  
Capillary Suction ◽  
Acidic Fraction ◽  
The Relationship

The occurrence of Transparent Exopolymer Particles (TEP), an acidic fraction of polysaccharides, was monitored for more than six months in the activated sludge of three MBR units, and the relationship between TEP and other fouling indicators was studied. These compounds consist mainly of exopolysaccharides of a sticky nature, a characteristic which makes them a group of interesting substances in processes like sedimentation, flocculation and membrane fouling. The relationship between capillary suction time (CST) and polysaccharides (PS) was linear for the three tested sludges, although the correlation with TEP concentrations was stronger. A slight linear correlation of both TEP and PS was found with the critical flux (CF) measured with a small filtration test cell, which was submerged in the membrane tank to assess the filterability performance of the sludge in situ. However, the correlation CF-PS was clearer. The relationship between TEP, polysaccharides and sludge filterability highlights the potential of this parameter for the monitoring of membrane systems.

A cost optimization study of flux and fouling rate for UF in the water industry

2008 ◽  
Vol 8 (1) ◽  
pp. 113-120 ◽  
Author(s):  
G. K. Pearce
Keyword(s):  
Membrane Fouling ◽  
Cost Optimization ◽  
Plant Size ◽  
Operating Pressure ◽  
High Flux ◽  
Chemical Cleaning ◽  
Critical Flux ◽  
Membrane Area ◽  
Optimization Study ◽  
The Relationship

Designing a commercial UF/MF system is an exercise in compromise. Selecting a high flux reduces capex by minimizing the membrane area required, but increases operating costs due to the increased chemical cleaning frequency, higher waste disposal volumes, and higher operating pressure. Most commercial systems are designed to run at fluxes significantly above the critical flux, so a degree of fouling and a reliance on chemical cleaning is inherent to the design. This paper examines the relationship between flux and membrane fouling rate through a review of experimental field data. The analysis shows that fouling rate increases exponentially with flux, with a function dependent upon the characteristics of the feed. The paper then presents the results of a cost optimization study in which Total Water Cost (TWC) is evaluated as a function of feed source and plant size for different CIP cleaning frequencies. The minimum TWC occurs in all cases for CIP frequencies of between 1/week and 1/month. Smaller plants with low fouling feeds have an optimum near 1 CIP/week using a relatively high flux design. In contrast, feeds with higher fouling propensity, and medium or large plant sizes have a TWC optimum close to 1 CIP/month, and should use a lower design flux. It is suggested that the flux corresponding to the TWC optimum should be designated the sustainable flux.

The relationship between critical flux and fibre movement induced by bubbling in a submerged hollow fibre system

2005 ◽  
Vol 51 (6-7) ◽  
pp. 115-122 ◽  
Author(s):  
F. Wicaksana ◽  
A.G. Fan ◽  
V. Chen
Keyword(s):  
Membrane Fouling ◽  
Hollow Fibre ◽  
Transmembrane Pressure ◽  
Feed Concentration ◽  
Critical Flux ◽  
Improved Performance ◽  
Qualitative Relationship ◽  
The Relationship ◽  
Mechanical Movement ◽  
Fibre Characteristics

Bubbling has been used to enhance various processes. In this paper we deal with the effect of bubbling on submerged hollow fibre membranes, where bubbling is applied to prevent severe membrane fouling. Previous work with submerged hollow fibres has observed that significant fibre movement can be induced by bubbling and that there is a qualitative relationship between fibre movement and filtration performance. Therefore, the aim of the present research has been to analyse the link between bubbling, fibre movement and critical flux, identified as the flux at which the transmembrane pressure (TMP) starts to rise. Tests were performed on vertical isolated fibres with a model feed of yeast suspension. The fibres were subject to steady bubbling from below. The parameters of interest were the fibre characteristics, such as tightness, diameter and length, as well as feed concentration. The results confirmed that the critical fluxes are affected by the fibre characteristics and feed concentration. Higher critical flux values can be achieved by using loose fibres, smaller diameters and longer fibres. The enhancement is partially linked to fibre movement and this is confirmed by improved performance when fibres are subject to mechanical movement in the absence of bubbling.

Flux-step method for the assessment of operational conditions in a submerged membrane bioreactor

2016 ◽  
Vol 73 (9) ◽  
pp. 2222-2230 ◽  
Author(s):  
Ezio Ranieri ◽  
Vito Goffredo ◽  
Mariachiara Campanella ◽  
Michael W. Falk
Keyword(s):  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Pressure Variation ◽  
Operating Conditions ◽  
Short Term ◽  
Step Method ◽  
Operational Conditions ◽  
Submerged Membrane Bioreactor ◽  
Separation Membrane ◽  
Solids Separation

A flux-step method was used for monitoring the pressure variation in a solids separation membrane at different operating conditions. A submerged membrane bioreactor pilot plant, used during the short-term tests, was used to purify actual restaurant wastewater. The influence of membrane backwash and relaxation on the variation of pressure variation was also evaluated. In order to reduce the deposition of irreversible fouling, the authors modified the literature-supported filtration to backwash cycling with filtration and relaxation cycling. The trials maintained a constant filtration to relaxation ratio that was in line with optimal filtration to backwashing ratios found in the literature. The relaxation cycling between two constant flux-steps effectively counteracted membrane fouling and the excessive decrease in average pressure, and it results in a lower waste of energy and water than a backwashing strategy.

scholarly journals Critical flux investigation in treating o/w emulsion by TiO2/Al2O3-PVDF UF membrane

2017 ◽  
Vol 76 (10) ◽  
pp. 2785-2792 ◽  
Author(s):  
Xuesong Yi ◽  
Yong Wang ◽  
Limei Jin ◽  
Wenxin Shi
Keyword(s):  
Membrane Fouling ◽  
High Efficiency ◽  
Pure Water ◽  
Membrane System ◽  
Transmembrane Pressure ◽  
Step Method ◽  
Critical Flux ◽  
Zero Rate ◽  
Long Time

Abstract A standard transmembrane pressure (TMP) step method has been used in membrane fouling assessment in tube ultrafiltration (UF) membrane system treating oil water (o/w) emulsion operated at constant TMP. Three flux reduction curve with different o/w concentration based on TMP variation were concluded by experiment, then, to describe fouling behavior and identify the occurrence of fouling in the so-called critical flux. Furthermore, sub-critical and super-critical flux experiment with a long time was determined, and zero rate of flux reduction (dF/dt) was never found during the whole trial period, indicating that critical flux in o/w UF process with its strict definition could not be defined in this paper. However, quasi-critical flux exists, under which the pollution rate was very slow. Moreover, a high-efficiency four steps cleaning method: mechanic scraping, pure water wash, pure water reverse wash, and dosing cleaning, was explored. It concluded that critical flux in real o/w UF system determined by TMP-step method can be used to predict long-term critical behavior with useful data on fouling propensity.

Evaluation of the Efficacy of ST2 and NT-proBNP in the Diagnosis and Prediction of Short- Term Prognosis in Heart Failure with Reduced Ejection Fraction

2017 ◽  
Vol 9 (04) ◽  
Author(s):  
Shivananda B Nayak ◽  
Dharindra Sawh ◽  
Brandon Scott ◽  
Vestra Sears ◽  
Kareshma Seebalack ◽  
...  
Keyword(s):  
Heart Failure ◽  
Ejection Fraction ◽  
Cardiac Biomarkers ◽  
Double Blind Study ◽  
Short Term ◽  
Double Blind ◽  
Reduced Ejection Fraction ◽  
The Mean ◽  
Design And Methods ◽  
The Relationship

Purpose: i) To determine the relationship between the cardiac biomarkers ST2 and NT-proBNP with ejection fraction (EF) in heart failure (HF) patients. ii) Assess whether a superiority existed between the aforementioned cardiac markers in diagnosing the HF with reduced EF. iii) Determine the efficacy of both biomarkers in predicting a 30-day cardiovascular event and rehospitalization in patients with HF with reduced EF iv) To assess the influence of age, gender, BMI, anaemia and renal failure on the ST2 and NT-proBNP levels. Design and Methods: A prospective double-blind study was conducted to obtain data from a sample of 64 cardiology patients. A blood sample was collected to test for ST2 and NT-proBNP. An echocardiogram (to obtain EF value), electrocardiogram and questionnaire were also obtained. Results: Of the 64 patients enrolled, 59.4% of the population had an EF less than 40%. At the end of the 30- day period, 7 patients were warded, 37 were not warded, one died and 17 were non respondent. Both biomarkers were efficacious at diagnosing HF with a reduced EF. However, neither of them were efficacious in predicting 30-day rehospitalization. The mean NT-proBNP values being: not rehospitalized (2114.7486) and 30 day rehospitalization (1008.42860) and the mean ST2 values being: not rehospitalized (336.1975), and 30-day rehospitalization. (281.9657). Conclusion: Neither ST2 or NT-proBNP was efficacious in predicting the short- term prognosis in HF with reduced EF. Both however were successful at confirming the diagnosis of HF in HF patients with reduced EF.

Validation of On-line Respiration Meter and its Applications by Computer Simulation

1992 ◽  
Vol 26 (5-6) ◽  
pp. 1355-1363 ◽  
Author(s):  
C-W. Kim ◽  
H. Spanjers ◽  
A. Klapwijk
Keyword(s):  
Steady State ◽  
Activated Sludge ◽  
Respiration Rate ◽  
Oxygen Demand ◽  
Operating Conditions ◽  
Mass Balances ◽  
Short Term ◽  
Respiration Rates ◽  
On Line ◽  
Made In

An on-line respiration meter is presented to monitor three types of respiration rates of activated sludge and to calculate effluent and influent short term biochemical oxygen demand (BODst) in the continuous activated sludge process. This work is to verify if the calculated BODst is reliable and the assumptions made in the course of developing the proposed procedure were acceptable. A mathematical model and a dynamic simulation program are written for an activated sludge model plant along with the respiration meter based on mass balances of BODst and DO. The simulation results show that the three types of respiration rate reach steady state within 15 minutes under reasonable operating conditions. As long as the respiration rate reaches steady state the proposed procedure calculates the respiration rate that is equal to the simulated. Under constant and dynamic BODst loading, the proposed procedure is capable of calculating the effluent and influent BODst with reasonable accuracy.

Plebiscitary Politics and the Threats to Legality

2019 ◽  
pp. 275-289
Author(s):  
Claudius Härpfer
Keyword(s):  
The State ◽  
Short Term ◽  
Political Processes ◽  
The Face ◽  
State Of Affairs ◽  
The Relationship

In recent times we find many plebiscitary acts that seek to democratically legitimize political processes in any direction. They have in common that they interrupt the normal routine of representative democracies to a certain degree and create an extra-daily state of affairs, which entails not only direct but also indirect consequences. The text attempts to systematize some of these mechanisms from a Weberian perspective using Brexit as an example. After a brief overview of Weber’s short-term politically inspired statements on plebiscitary democracy, the text systematizes Weber’s understanding of the state as a bureaucratic apparatus that requires any kind of leader to be controlled. Subsequently, the text discusses the relationship between domination, legality, and rationality in order to finally point out the danger of erosion of truth and legality through the emergence of competing consensus communities in the face of competing conceptions of order.

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