Formation and breakage of flocs using dual polymers

2006 ◽  
Vol 53 (7) ◽  
pp. 217-223 ◽  
Author(s):  
M.A. Yukselen ◽  
J. Gregory ◽  
E. Soyer
Keyword(s):  
Shear Rate ◽  
Test Procedure ◽  
Optical Monitoring ◽  
Ionic Polymers ◽  
Ionic Polymer ◽  
Polymer Addition ◽  
Anionic Polymers ◽  
Jar Test ◽  
Average Shear ◽  
Floc Strength

The effect of shear on the formation and break-up of flocs generated using cationic, anionic and non-ionic polymers, and dual combinations of these, has been investigated using conventional jar test procedure and by continuous optical monitoring. The breakage of flocs was followed at a high stirring speed, corresponding to average shear rate (G) of approximately 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 of 50 rpm (G≈23 s−1) to allow the flocs to regrow. For cationic–anionic polymers case, the regrowth of flocs was fully reversible and the breakage factors were smallest indicating highest floc strength. In contrast, flocs formed using non-ionic polymer together with anionic or cationic did not produce as strong flocs. It is found that the sequence of polymer addition is not very significant for floc formation and reformation when the cationic–anionic dual system is used.

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.

The use of selective and direct DAF for removal of particulate contaminants in drinking water treatment

1995 ◽  
Vol 31 (3-4) ◽  
pp. 49-57 ◽  
Author(s):  
James P. Malley
Keyword(s):  
Drinking Water ◽  
Drinking Water Treatment ◽  
Cationic Polymers ◽  
Ionic Polymers ◽  
Charge Reversal ◽  
Dissolved Air Flotation ◽  
Polymer Addition ◽  
Anionic Polymers ◽  
Particulate Contaminants ◽  
Dissolved Air

Cationic polymers were found to coat bubbles resulting in charge reversal and increasingly positive EPM. Batch bench-scale dissolved air flotation (DAF) studies show promising benefits from the addition of cationic or non-ionic polymers to the saturated recycle line of conventional DAF. In cases where low turbidity, low color waters are being treated, direct DAF compared well with conventional DAF. Polymer addition improved the percentage solids of the float. Anionic polymers were not found to be effective. Further research at the pilot and full-scale is needed to verify these findings.

The effect of polymeric flocculants on floc strength and filter performance

2006 ◽  
Vol 53 (7) ◽  
pp. 77-85 ◽  
Author(s):  
M.M. Rawlings ◽  
C.S.B. Fitzpatrick ◽  
J. Gregory ◽  
A. Wetherill
Keyword(s):  
Water Treatment ◽  
Test Procedure ◽  
Dissolved Air Flotation ◽  
Flotation Process ◽  
Filter Performance ◽  
Water Treatment Process ◽  
Jar Test ◽  
Floc Strength ◽  
Particle Counts ◽  
Photometric Dispersion

Polymeric flocculants are widely used throughout the water industry as flocculant aids, they are known to increase floc density and aid settlement in the clarification stage of the water treatment process. In this research, polymeric flocculants were used to improve floc strength prior to filtration on a dissolved air flotation (DAF) plant in an attempt to prevent filter breakthrough. A modified jar test procedure using a PDA (photometric dispersion analyser) optical flocculation monitor was developed in order to evaluate the system floc strength. Filtration trials were carried out on a pilot filter rig situated on a surface water treatment works in Yorkshire. The filter feed originated from the main plant filter channel. Filter performance was assessed by continuous online monitoring of effluent particle counts, turbidity and headloss over the period of the filter run. Results indicated that low doses of polymeric flocculants had a beneficial effect on filtered water quality, as measured by particle counts, turbidity, UV254 absorption and dissolved organic carbon (DOC). Polymeric flocculants also had the effect of extending filter run length. The modified jar test results indicated that the flocculants used improved the floc strength and enhanced reflocculation of the micro flocs present after the flotation process.

scholarly journals INFLUENCE OF FLOCCULANT TYPE ON STRENGTH CHARACTERISTICS OF FLOCS IN CLAY-SALT SUSPENSIONS

2020 ◽  
Vol 63 (6) ◽  
pp. 30-36
Author(s):  
Olga R. Seredkina ◽  
Olesya V. Rakhimova ◽  
Sergey V. Lanovetskiy
Keyword(s):  
Strength Characteristics ◽  
Ionic Polymers ◽  
Partial Restoration ◽  
Anionic Polymers ◽  
Cationic Flocculant ◽  
Potential Possibility ◽  
Floc Strength ◽  
Cationic Copolymers ◽  
Hydrodynamic Effects ◽  
Flocculated Suspension

The results of studies on the effect of the flocculant type on the strength characteristics of floccules in clay-salt suspensions, obtained using a laser analyzer of particle size Lasentec D600L FBRM systems were presented in the article. The coefficients of strength and reduction of aggregates formed by polyacrylamide and its anionic and cationic copolymers were determined. Increasing the speed of mixing by using of polymers various types leads to the destruction of the formed aggregates in the flocculated suspension. The size of flocs induced by a cationic flocculant is reduced from 250 to 110 mm, for anionic and non-ionic flocculants - from 500 to 250 mm. The dependence of floc strength on the macromolecules adsorption mechanism on a solid surface was established. The decrease in hydrodynamic effects entails the partial restoration of floccules. It was shown that the recovery of flocs for all studied polymers was limited, which indicates a significant irreversibility of the aggregates destruction process. When using cationic flocculant, the ability to restore the aggregates is 2.5 times lower compared to anionic and non-ionic polymers. For nonionic and anionic polymers, the dependence of flocs coefficients of strength and recovery on the flocculant dosage was established. Dosage of cationic polymer does not affect these indicators. The dynamics of flocculation, destruction and reflocculation processes using various flocculants was considered. The influence of the charge type and polymer consumption on the mechanism of particles interaction was established. The potential possibility of using the obtained results to improve the technology of potassium chloride production at the stages of thickening and dehydrating clay-salt sludge was shown.

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.

scholarly journals Use of helical ribbon mixer for measurement of rheological properties of fruit pulps

2013 ◽  
Vol 19 (No. 4) ◽  
pp. 148-153 ◽  
Author(s):  
P. Novotná ◽  
A. Landfeld ◽  
K. Kýhos ◽  
M. Houška ◽  
J. Strohalm
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Flow Behaviour ◽  
Rotational Rheometer ◽  
Shear Rates ◽  
Coaxial Cylinders ◽  
Helical Ribbon ◽  
Flow Behaviour Index ◽  
Average Shear ◽  
Behaviour Index

Fruit pulps contain fine particles of the flesh of the original fruit that are suspended in the fruit juice. This suspension has a tendency to settling or separation during measurements of its rheological properties in the rotational rheometer with coaxial cylinders (especially if the greater gap is used). In this case the use of a mixer is convenient. The mixer can serve as a tool for measurement of rheological properties and at the same time it can prevent the settling and it is not sensitive to the occurrence of greater particles in the measured fluid. The helical ribbon mixer was used in this work for measurement of five samples of fruit pulp. The mixer was calibrated by the use of Newtonian fluid of known viscosity (honey). The radius of the inner cylinder of hypothetical rotational rheometer was predicted from the assumption that mixer and cylinder exhibit the same torque necessary for the rotation at the same rotational speed. The average shear rate in the mixed pulp was predicted by using the relation valid for power law fluids and rheometer with coaxial cylinders. The radius (where the average shear rate was calculated) was chosen by the requirement that the shear rate would be almost independent of changes in the flow behaviour index valid for measured pulps. Firstly the flow behaviour index was predicted as a slope of torque vs. rotational speed dependence in log-log co-ordinates. It was found that the flow behaviour index varies in the range 0.2–0.3. The radius was predicted from a graph where shear rates for 0.2 and 0.3 are the same. Then the average shear rates were calculated from rotational speeds for individual flow behaviour indexes. Rheological properties measured by using a mixer correspond to those measured with a rotational rheometer with coaxial cylinders satisfactorily only in the case that the creeping flow regime was kept in the mixed fluid. The fruit pulps are strongly non-Newtonian fluids with very low values of the flow behaviour index around 0.2.

A Dynamic Wall Shear Stress Sensor Based on Ionic Polymers

2005 ◽  
Author(s):  
A. Etebari ◽  
M. D. Bennett ◽  
D. J. Leo ◽  
P. P. Vlachos
Keyword(s):  
Signal To Noise Ratio ◽  
Calibration Procedure ◽  
Ionic Polymers ◽  
Time Resolved ◽  
Ionic Polymer ◽  
Polymer Sensors ◽  
Friction Measurements ◽  
Dynamic Time ◽  
Compensation Approach

This paper presents the first implementation of a novel class of dynamic time-resolved direct skin friction measurements sensor based on active ionic polymer transducers. These ionic polymer sensors have the advantage that they contain no moving parts, perform a direct measurement of shear, and can be mounted directly to the surface of an existing vessel with no modification. During the present effort we characterize the accuracy of the sensors and validate their dynamic measurement response. Using an oscillating Stokes layer calibration procedure we demonstrate measurement accuracy in fluctuating shear on the order of 4.92% over a range of stresses of +/- 3 Pa and signal-to-noise-ratio on the order of 60 dB. The frequency response of the sensor is over 10 kHz however due to experimental limitations we were not able to calibrate for frequencies higher than 140 Hz. These sensors have been shown to be insensitive to vibration or pressure. Also, an automatic change of impedance compensation approach is proposed that allows in-situ recalibration of the sensors and accounts for environmental effects such as changes of temperature on the sensors performance. The results demonstrate the potential for using ionic polymer sensors to perform accurate, high frequency measurements of shear in turbulent boundary layers.

Measurement of the average shear rate around a microparticle in the shear thinning medium with laser tweezers

2017 ◽  
Vol 36 (5) ◽  
pp. 529-533
Author(s):  
Piotr Domagalski ◽  
Marek Dziubinski ◽  
Ryszard Pawlak ◽  
Mariusz Tomczyk
Keyword(s):  
Shear Rate ◽  
Shear Thinning ◽  
Laser Tweezers ◽  
Average Shear Rate ◽  
Average Shear

Computational Micromechanics Analysis of Ionic Polymers With Cluster Morphology

Aerospace ◽  
2004 ◽  
Author(s):  
Lisa Mauck Weiland ◽  
Donald J. Leo
Keyword(s):  
Mechanical Response ◽  
Computational Study ◽  
Response Force ◽  
Ionic Polymers ◽  
Ion Distribution ◽  
Mechanical Stiffness ◽  
Ionic Polymer ◽  
Charge Imbalance ◽  
The Impact ◽  
Computational Micromechanics

In recent years there has been considerable study of the potential mechanisms underlying the electro-mechanical response of ionic-polymer-metal composites (IPMCs). Most of these efforts have employed assumptions of uniform and balanced ion distribution within spherical cluster shapes, in the ionic polymer layer of the IPMC. Inspired by the results of a preliminary computational study, the present work investigates the impact of dispensing with these assumptions. A computational micromechanics model has been developed to study ion response in a single cluster of these ionomeric transducers. Assuming a constant solvated state, the model tracks the position of individual ions within a given cluster in response to ion-ion interaction, mechanical stiffness of the pendant chain, cluster surface response force, and external electric field loading. Results suggest that the classic assumptions will tend to under-predict electromechanical response and that charge imbalance has significant impact of cluster behavior.

Magnesium Induced Algal Flocculation in a Fluidized Bed

1991 ◽  
Vol 23 (7-9) ◽  
pp. 1695-1702 ◽  
Author(s):  
S. Elmaleh ◽  
J. Coma ◽  
A. Grasmick ◽  
L. Bourgade
Keyword(s):  
Pressure Drop ◽  
Fluidized Bed ◽  
Suspended Solids ◽  
Energy Requirement ◽  
Test Procedure ◽  
Total Suspended Solids ◽  
Oxidation Pond ◽  
Waste Sludge ◽  
Jar Test ◽  
Solids Separation

The effectiveness of the use of seawater and of magnesium in the removal of microalgae from oxidation pond effluents was investigated using the jar test procedure. The results indicated that the major flocculating reaction is the magnesium hydroxide precipitation at pH 11.5. The next step was to intensify the liquid-solids separation by use of a fluidized bed flocculator packed with 800 µm inert resin particles provided with an inclined multitubular settler. The total suspended solids abatement could reach 95 % with a superficial upflow velocity of 30 m/h corresponding to a residence time through the whole unit of 5 minutes only. The energy requirement quantified by the pressure drop through the bed is very low. Besides, the waste sludge extracted from the settler is easily thickened.

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