Dynamic testing of water treatment coagulants

2001 ◽  
Vol 1 (4) ◽  
pp. 65-72 ◽  
Author(s):  
J. Gregory ◽  
L. Rossi
Keyword(s):  
Mode Of Action ◽  
Dynamic Testing ◽  
Test Procedure ◽  
Aluminium Sulphate ◽  
Jar Test ◽  
Iron Salts ◽  
Flow Through ◽  
Preliminary Study ◽  
Selection For ◽  
Empirical Approaches

Pre-polymerised inorganic coagulants, such as polyaluminium chloride (PAC) have several advantages over conventional aluminium and iron salts. However, their mode of action is not fully understood and progress in this area has been made largely by empirical approaches. In this preliminary study we have followed the dynamics of flocculation of model clay/humic acid suspensions following the addition of three different coagulants: aluminium sulphate and two commercial PAC products. Experiments were conducted using controlled stirring rates in a modified jar test procedure, in which the formation and break-up of flocs could be monitored continuously by a flow-through optical technique. The results show significant differences in the behaviour of the coagulants and one of the PAC samples gives much larger and stronger flocs. Further experiments along these lines should help to elucidate the mode of action of different forms of coagulant and to aid in their selection for specific applications.

Properties of flocs formed using different coagulants

2002 ◽  
Vol 2 (5-6) ◽  
pp. 95-101 ◽  
Author(s):  
M.A. Yukselen ◽  
J. Gregory
Keyword(s):  
Shear Rate ◽  
Continuous Monitoring ◽  
Test Procedure ◽  
Cationic Polyelectrolyte ◽  
Aluminium Sulphate ◽  
Jar Test ◽  
Average Shear ◽  
Break Up ◽  
Polyaluminium Chloride ◽  
Floc Breakage

The effects of shear on the formation and break-up of flocs generated using aluminium sulphate (“alum”), polyaluminium chloride and a cationic polyelectrolyte have been investigated using conventional jar test procedure and by continuous optical monitoring. Using the experimentally determined optimum dosage, the breakage of flocs was followed at a high stirring speed, corresponding to average shear rate (G) of about 330-520 s-1. Most of the breakage occurred within a few seconds of increasing the shear rate. After each breakage the stirring rate was reduced to the original value to allow the flocs to re-grow. For alum and polyaluminium chloride, it was found that only limited re-growth of flocs occurred indicating a significant irreversibility of the floc break-up process. Residual turbidity increased after floc breakage and re-growth, indicating a reduction in sedimentation rate of the re-grown flocs, consistent with the continuous monitoring results. For the cationic polyelectrolyte, the re-growth of flocs occurred to a much greater extent and floc breakage was almost fully reversible.

Properties of flocs produced by water treatment coagulants

2001 ◽  
Vol 44 (10) ◽  
pp. 231-236 ◽  
Author(s):  
J. Gregory ◽  
V. Dupont
Keyword(s):  
Test Procedure ◽  
Dynamic Monitoring ◽  
Optical Technique ◽  
Water And Wastewater Treatment ◽  
Aluminium Sulfate ◽  
Jar Test ◽  
Water And Wastewater ◽  
Clay Suspensions ◽  
Polyaluminium Chloride ◽  
Floc Breakage

Hydrolyzing coagulants are extensively used in water and wastewater treatment, often under conditions where hydroxide precipitation is important, giving “sweep flocculation”. Pre-hydrolyzed coagulants, such as polyaluminium chloride (PACl) are also widely used and have several advantages over traditional additives, such as aluminium sulfate. Their action is usually discussed in terms of cationic species and charge neutralization. However, precipitation may also be important and this aspect has not been considered in detail. The present work has compared the action of alum and three commercial PACl products on model clay suspensions. The conventional jar test procedure has been used, along with measurements of settled floc volume and dynamic monitoring of floc formation and break-up by an optical technique. The latter method gives very useful information on the nature of the flocs produced and their response to different shear conditions. It is clear from the results that the PACl products form larger and stronger flocs than alum. With all coagulants floc breakage appears to be essentially irreversible. Sediment volumes are slightly lower for flocs produced by PACl than by alum, but the value is proportional to the dosage in all cases.

The Gas Permeability of Plasma Sprayed Ceramic Coatings

1997 ◽  
Author(s):  
A.C. Fox ◽  
T.W. Clyne
Keyword(s):  
Gas Permeability ◽  
Test Procedure ◽  
Ceramic Coatings ◽  
Hydrogen Gas ◽  
Steady State Flow ◽  
Flow Rates ◽  
Specific Permeability ◽  
Measured Flow ◽  
Flow Through ◽  
Plasma Sprayed

Abstract A simple test procedure, based on steady state flow through a membrane, has been developed for measurement of the gas permeability of specimens over a range of temperature. The reliability of this equipment has been verified by testing solid disks containing single perforations and comparing the measured flow rates with those expected on the basis of laminar flow. Coatings of yttria-stabilised zirconia have been produced by plasma spraying in vacuum and in air. The specific permeability of these coatings has been measured at temperatures ranging up to 600°C, using hydrogen gas. It has been found that permeability is increased for coatings produced with longer stand-off distances and at higher pressures. Porosity levels have been measured using densitometry and microstructural features have been examined using SEM. A model has been developed for prediction of the permeability from such microstructural features, based on percolation theory. Agreement between predicted and measured permeabilities is good, although it is clear that more comprehensive data are needed in order to validate the model systematically.

Abstract 309: Vasovasorum Volume Can Be Measured by Contrast-Enhanced 3D Carotid Duplex Ultrasound: Concept and Design of a Novel Method for Predicting Stroke Risk in Patients With Carotid Artery Stenosis

2014 ◽  
Vol 34 (suppl_1) ◽  
Author(s):  
Isibor J Arhuidese ◽  
Alexander Nodel ◽  
Umair Qazi ◽  
Diana Call ◽  
Bruce Perler ◽  
...  
Keyword(s):  
Stroke Risk ◽  
Duplex Ultrasound ◽  
Population Based ◽  
Severe Stenosis ◽  
Asymptomatic Patients ◽  
Grant Support ◽  
Contrast Enhanced ◽  
Novel Method ◽  
Preliminary Study ◽  
Selection For

Introduction: Stroke remains a leading cause of death and disability. The reliance on the occurrence of symptoms and degree of stenosis for selecting patients with carotid stenosis for intervention is not ideal because it is often seen that patients with severe stenosis remain asymptomatic while many patients with moderate stenosis experience stroke. Furthermore, the majority of patients are asymptomatic until they experience stroke. It is known that intimal neovascularization flourishes as atherosclerotic disease progresses; however no technique in current use adequately correlates neovascularization to stroke risk. Objective: With seed grant support from the Society for Vascular Surgery Foundation we are executing a study based on our hypothesis that Vasovasorum Volume (VVV) measured using CE-3DCDU as a valid tool for mapping stroke risk. Method: We are recruiting symptomatic and asymptomatic patients adjudged to have >50% and >70% stenosis respectively on routine duplex ultrasound. Vasovasorum volume is measured using CE-3DCDU in patients who are eligible for carotid endarterectomy. Plaque removed during surgery is marked, decalcified and immunostained with CD34. Thereafter, VVV is measured in the excised plaque using 3D reconstruction histometry. We then evaluate the reliability and accuracy of CE-3DCDU in relation to the histopathology and compare VVV in symptomatic and asymptomatic patients. Results: The preliminary study included six patients and the results show that VVV measurement in carotid ultrasound and histopathology is feasible and reproducible (Figures 1 and 2). Conclusion: Vasovasorum volume is a promising predictor of stroke risk. By identifying patients who are truly at high risk for stroke, VVV measured by CE-3DCDU will aid precise patient selection for intervention, thus prevent stroke, save lives, limit disability and expend health care resources in an informed manner. The next phase of this project involves the establishment of efficacy and a population based multi-center clinical trial to generate evidence required to incorporate VVV measured using CE-3DCDU into clinical practice.

scholarly journals Static and Fatigue Tests on Cementitious Cantilever Beams Using Nanoindenter

Micromachines ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 630 ◽  
Author(s):  
Yidong Gan ◽  
Hongzhi Zhang ◽  
Branko Šavija ◽  
Erik Schlangen ◽  
Klaas van Breugel
Keyword(s):  
Cement Paste ◽  
Fracture Behaviour ◽  
Test Procedure ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Cantilever Beams ◽  
Fundamental Properties ◽  
Micromechanical Properties ◽  
Preliminary Study ◽  
Binding Component

Cement paste is the main binding component in concrete and thus its fundamental properties are of great significance for understanding the fracture behaviour as well as the ageing process of concrete. One major aim of this paper is to characterize the micromechanical properties of cement paste with the aid of a nanoindenter. Besides, this paper also presents a preliminary study on the fatigue behaviour of cement paste at the micrometer level. Miniaturized cantilever beams made of cement paste with different water/cement ratios were statically and cyclically loaded. The micromechanical properties of cement paste were determined based on the measured load-displacement curves. The evolution of fatigue damage was evaluated in terms of the residual displacement, strength, and elastic modulus. The results show that the developed test procedure in this work is able to produce reliable micromechanical properties of cement paste. In addition, little damage was observed in the cantilever beams under the applied stress level of 50% to 70% for 1000 loading cycles. This work may shed some light on studying the fatigue behaviour of concrete in a multiscale manner.

scholarly journals Model Selection for Univariable Fractional Polynomials

2017 ◽  
Vol 17 (3) ◽  
pp. 619-629 ◽  
Author(s):  
Patrick Royston
Keyword(s):  
Test Procedure ◽  
Selection Procedure ◽  
Real Data ◽  
Parametric Modeling ◽  
Royal Statistical Society ◽  
Fractional Polynomials ◽  
Fractional Polynomial ◽  
Polynomial Models ◽  
Selection For ◽  
Function Selection

Since Royston and Altman's 1994 publication ( Journal of the Royal Statistical Society, Series C 43: 429–467), fractional polynomials have steadily gained popularity as a tool for flexible parametric modeling of regression relationships. In this article, I present fp_select, a postestimation tool for fp that allows the user to select a parsimonious fractional polynomial model according to a closed test procedure called the fractional polynomial selection procedure or function selection procedure. I also give a brief introduction to fractional polynomial models and provide examples of using fp and fp_select to select such models with real data.

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