kaolinite and aluminum-sulfate

The addition of powdered activated carbon (PAC) to remove micropollutants is a commonly used technology to improve drinking water quality. However, the effects of PAC dosing strategy on the coagulation-flocculation process of water treatment have not been well understood, especially for water with low amounts of inorganic particles. Therefore, the current research aimed to comprehensively study the effects of simultaneous addition of PAC and aluminum sulfate (AS) coagulants (denoted as PAC-AS) or adding PAC 2 h before coagulation (denoted as PAC2h-AS) on the coagulation behavior in humic acid (HA) and HA-kaolin water treatment. The results showed that the floc size, growth rate, breakage factor, and fractal dimension were all enhanced by PAC-AS and PAC2h-AS for HA but not for HA-kaolin water treatment. In HA water treatment, PAC-AS reached a larger floc size and faster growth rate, while PAC2h-AS achieved a larger floc breakage factor and fractal dimension value. For PAC2h-AS, the pre-adsorption of HA onto PAC would lower the initial particle concentration and reduce the collision probability during HA water coagulation process; thus, the DOC removal efficiency, floc size, and growth rate of PAC2h-AS were relatively smaller than those of PAC-AS. For the floc strength and floc fractal dimension, the pre-adsorption of HA onto PAC contributed to formation of stronger inter-particle bonds; thus, stronger and more compact flocs were formed by PAC2h-AS compared with those of PAC-AS. The addition of PAC had a smaller impact on the floc properties in HA-kaolin water treatment owing to its higher initial particle concentration.

Topics: Adsorption; Alum Compounds; Charcoal; Flocculation; Fractals; Humic Substances; Kaolin; Powders; Water Purification

The growth rate and size of floc formation is of great importance in water treatment especially in coagulation process. The floc formation kinetics and the coagulation efficiency of synthetic water were investigated by using an on-line continuous optical photometric dispersion analyze and the analysis of water quality. Experimental conditions such as alum dosage, pH value for coagulation, stirring intensity and initial turbidity were extensively examined. The photometric dispersion analyze results showed that coagulation of kaolin suspensions with two coagulants (alum and polyaluminium chloride) could be taken as a two-phase process: slow and rapid growth periods. Operating conditions with higher coagulant doses, appropriate pH and average shear rate might be particularly advantageous. The rate of overall floc growth was mainly determined by a combination of hydraulic and water quality conditions such as pH and turbidity. The measurement of zeta potential indicates that polyaluminium chloride exhibited higher charge-neutralizing ability than alum and achieved lower turbidities than alum for equivalent Al dosages. Under the same operating conditions, the alum showed a higher grow rate, but with smaller floc size.

Topics: Alum Compounds; Aluminum Hydroxide; Flocculation; Hydrogen-Ion Concentration; Kaolin; Nephelometry and Turbidimetry; Water Purification

The compound bioflocculant (CBF)-aluminum sulfate (AS) dual-coagulant and AS were comparatively studied for the coagulation of kaolin-humic acid solution. Floc properties including floc growth rate, size, strength, recoverability and fractal dimension under different pH conditions were investigated by Mastersizer 2000. Results indicated that, the flocs formed by AS-CBF (AS dosed first) showed the largest size and the best recoverability across the pH range investigated. While flocs formed by CBF-AS gave the most compact structure. The three coagulants exhibited similar floc growth rate and strength. Moreover, flocs formed in acidic conditions were stronger and more recoverable but showed lower growth rate, smaller size and looser structure compared to those formed at pH>6 regardless of the coagulant used. Charge neutralization was the dominant mechanism for AS at low pH, while the coagulation mechanism transformed to enmeshment as the pH increased. There was an additional adsorption bridging effect for AS-CBF and CBF-AS.

Topics: Alum Compounds; Flocculation; Fractals; Humic Substances; Hydrogen-Ion Concentration; Kaolin; Particle Size; Solutions

The fractionation and measurement of residual aluminum was conducted during the treatment of humic (HA)-kaolin synthetic water with Al(2)(SO(4))(3), AlCl(3) and polyaluminum chloride (PAC) in order to investigate the effect of pH on the coagulation performance as well as residual aluminum speciation. Experimental results suggested that turbidity removal performance varied according to the following order: AlCl(3)>PAC>Al(2)(SO(4))(3). HA removal performance of PAC was better than that of AlCl(3) under acidic condition. The optimum pH range for AlCl(3) and Al(2)(SO(4))(3) was between 6.0 and 7.0 while PAC showed stable HA and UV(254) removal capacity with broader pH variation (5.0-8.0). For the three coagulants, majority of residual aluminum existed in the form of total dissolved Al (60-80%), which existed mostly in oligomers or complexes formed between Al and natural organic matter or polymeric colloidal materials. PAC exhibited the least concentration for each kind of residual aluminum species as well as their percentage in total residual aluminum, followed by AlCl(3) and Al(2)(SO(4))(3) (in increasing order). Moreover, PAC could effectively reduce the concentration of dissolved monomeric Al and its residual aluminum ratio was the least among the three coagulants and varied little at an initial pH between 7.0 and 9.0.

Topics: Alum Compounds; Aluminum; Aluminum Chloride; Aluminum Compounds; Chlorides; Humic Substances; Hydrogen-Ion Concentration; Kaolin; Linear Models; Spectrophotometry, Ultraviolet; Water Purification

The application of AlCl3, Al2 (SO4)3 and poly-aluminum chloride (PAC) in humic acid-kaolin simulated water was studied in this article. It is intended to discuss the relationship among coagulation effect of Al-based coagulants in humic acid-kaolin simulated water and content and speciation of residual aluminum. It was found that, the turbidity removal efficiency and UV254 removal efficiency could reach about 90% at the tested dosage. At higher dosage, PAC gave better coagulation effect. The residual total aluminum content and residual aluminum ratio of PAC, which was 0.9 mg/L and - 3.0% or so respectively, were greatly lower than those of AlCl3 and Al2 (SO4)3. The residual total dissolved aluminum was the predominant content in the effluent after coagulation and sedimentation by the three Al-based coagulants. For the total dissolved aluminum, the proportion of dissolved organic aluminum was significantly higher than that of other aluminum speciation. With respect to humic acid-kaolin simulated water, the content of residual total aluminum in the effluent after coagulation and sedimentation by PAC decreased obviously compared to AlCl3 and Al2 (SO4)3. PAC could effectively decrease the content of residual dissolved aluminum speciation which has higher toxicity. The content of residual total dissolved aluminum in the effluent after coagulation and sedimentation by PAC was about 0.6 mg/L.

Topics: Alum Compounds; Aluminum; Aluminum Chloride; Aluminum Compounds; Aluminum Hydroxide; Chlorides; Flocculation; Humic Substances; Kaolin; Water Pollutants, Chemical; Water Purification; Water Supply

Methods for monitoring particle aggregation are briefly reviewed. Most of the techniques are based on some form of light scattering and may be greatly dependent on the optical properties of aggregates, which are not generally known. As fractal aggregates grow larger their density can become very low and this has important practical consequences for light scattering. For instance, the scattering coefficient may be much less than for solid objects, which means that the aggregates can appear much smaller than their actual size by a light transmission method. Also, for low-density objects, a high proportion of the scattered light energy is within a small angle of the incident beam, which may also be relevant for measurements with aggregates. Using the "turbidity fluctuation" technique as an example, it is shown how the apparent size of hydroxide flocs depends mainly on the included impurity particles, rather than the hydroxide precipitate itself. Results using clay suspensions with hydrolyzing coagulants and polymeric flocculants under different string conditions are discussed.

Topics: Alum Compounds; Aluminum Silicates; Clay; Ferric Compounds; Flocculation; Fractals; Hydroxides; Kaolin; Light; Nephelometry and Turbidimetry; Particle Size; Scattering, Radiation; Water

Dissolved air flotation (DAF) is a method for removing particles from water using micro bubbles instead of settlement. The process has proved to be successful and, since the 1960s, accepted as an alternative to the conventional sedimentation process for water and wastewater treatment. However, limited research into the process, especially the fundamental characteristics of bubbles and particles, has been carried out. The single collector collision model is not capable of determining the effects of particular characteristics, such as the size and surface charge of bubbles and particles. Han has published a set of modeling results after calculating the collision efficiency between bubbles and particles by trajectory analysis. His major conclusion was that collision efficiency is maximum when the bubbles and particles are nearly the same size but have opposite charge. However, experimental verification of this conclusion has not been carried out yet. This paper describes a new method for measuring the size of particles and bubbles developed using computational image analysis. DAF efficiency is influenced by the effect of the recycle ratio on various average floc sizes. The larger the recycle ratio, the higher the DAF efficiency at the same pressure and particle size. The treatment efficiency is also affected by the saturation pressure, because the bubble size and bubble volume concentration are controlled by the pressure. The highest efficiency is obtained when the floc size is larger than the bubble size. These results, namely that the highest collision efficiency occurs when the particles and bubbles are about the same size, are more in accordance with the trajectory model than with the white water collector model, which implies that the larger the particles, the higher is the collision efficiency.

Topics: Air; Alum Compounds; Flocculation; Kaolin; Particle Size; Pressure; Waste Disposal, Fluid; Water Purification

This study investigated whether colloid-sized particles can enmesh and protect viruses from 254-nm ultraviolet (UV) light and sought to determine the particle characteristics (e.g. size, chemical composition) that are most relevant in causing a protective effect. Two viral surrogates (MS2 coliphage and bacteriophage T4), three types of particles (kaolin clay, humic acid powder, and activated sludge), two coagulants (alum and ferric chloride), two filtration conditions (none and 0.45 microm), and two UV doses (40 and 80 mJ/cm2 for MS2 coliphage; 2 and 7 mJ/cm2 for bacteriophage T4) were considered in a series of bench-scale UV collimated beam experiments. Transmission electron microscopy was used to qualitatively confirm the phage particle-association after coagulation. Humic acid and activated sludge floc particles shielded both viral surrogates to a statistically significant degree (with >99% confidence) relative to particle-free control conditions, while the kaolin clay particles provided no significant protection. The results of the study suggest that particles <2 microm in diameter are large enough to protect viruses from UV light and that particulate chemical composition (e.g. UV-absorbing organic content) may be a critical factor in the survival of particle-associated viruses during UV disinfection.

Topics: Alum Compounds; Bacteriophage T4; Chlorides; Colloids; Disinfection; Ferric Compounds; Flocculation; Humic Substances; Kaolin; Levivirus; Microscopy, Electron, Transmission; Particle Size; Sewage; Ultraviolet Rays; Water Microbiology; Water Purification

Temperature is known to affect flocculation and filter performance. Jar tests have been conducted in the laboratory, using a photometric dispersion analyser (PDA) to assess the effects of temperature on floc formation, breakage and reformation. Alum, ferric sulphate and three polyaluminium chloride (PACI) coagulants have been investigated for temperatures ranging between 6 and 29 degrees C for a suspension of kaolin clay in London tap water. Results confirm that floc formation is slower at lower temperatures for all coagulants. A commercial PACl product, PAX XL 19, produces the largest flocs for all temperatures; and alum the smallest. Increasing the shear rate results in floc breakage in all cases and the flocs never reform to their original size. This effect is most notable for temperatures around 15 degrees C. Breakage, in terms of floc size reduction, is greater for higher temperatures, suggesting a weaker floc. Recovery after increased shear is greater at lower temperatures implying that floc break-up is more reversible for lower temperatures.

Topics: Alum Compounds; Aluminum Chloride; Aluminum Compounds; Aluminum Silicates; Chlorides; Clay; Coagulants; Ferric Compounds; Flocculation; Kaolin; Polymers; Temperature; Waste Disposal, Fluid

Arsenic removal from household drinking water has been receiving considerable attention in the field of water supply engineering. To develop the optimal coagulation protocol, the effectiveness of several operation options such as coagulants, coagulant aids and additives, as well as flocs separation systems were investigated in this study through the use of orthogonal array experiment based on Taguchi method. Arsenic removal mechanism during household coagulation (via manual mixing) was also discussed. The results showed that the addition of kaoline and powder activated carbon (PAC) did not enhance arsenic removal efficiency of ferric sulfate or aluminum sulfate. Similarly, mixture of ferric sulfate and aluminum sulfate (MFA) as well as polymeric ferric silicate sulfate (PFSiS) was also unable to improve the overall arsenic removal efficiency. The mechanism of arsenic removal during coagulation was somewhat different from those experienced in conventional processes. Coprecipitation appeared to be the crucial mechanism for arsenic removal. It is noted from this study that arsenic adsorption isotherm under household operation condition could be described by Langmuir equation. An efficient flocs separation system subsequent to coagulation was essential to achieve the effectiveness of overall arsenic removal. The results obtained from field experiment demonstrated that the method of ferric sulfate coagulation/sand filtration for arsenic removal from household drinking water was acceptable and affordable.

Topics: Alum Compounds; Arsenic; Carbon; Chemical Precipitation; Ferric Compounds; Flocculation; Housing; Humans; Kaolin; Water Movements; Water Pollutants; Water Purification

Aluminum is suspected to play a role in several neurological disorders. Reactive oxygen species (ROS) lead to oxidative stress, which is thought to be a possible mechanism for neurological damage. Interactions between aluminum and iron, a known promoter of prooxidant events, were studied in cerebral tissues using a fluorescent probe to measure rates of generation of ROS. Al2(SO4)3 alone failed to stimulate ROS production over a wide range of concentrations (50-1000 microM). The aluminum-deferrioxamine chelate in the absence of iron could also not potentiate ROS formation. However, Al2(SO4)3 potentiated FeSO4-induced ROS, with a maximal effect at 10 microM Fe and 500 microM Al. Kaolin, a hydrated aluminum silicate, did not potentiate iron-induced ROS formation. Ferritin had a minor stimulatory effect on ROS generation, but this was not potentiated by the concurrent presence of Al2(SO4)3. Transferrin had no effect on basal rates of ROS generation, but when Al2(SO4)3 was also present, ROS production was enhanced. It is concluded that: 1. There is a potentiation of iron-induced ROS by aluminum salts; 2. Free or complexed aluminum alone is not a key producer of ROS; and 3. High rates of ROS production are unlikely to be owing to the displacement by aluminum iron from its biologically sequestered locations.

Topics: Alum Compounds; Animals; Drug Synergism; Ferric Compounds; Ferritins; Fluoresceins; Kaolin; Male; Nerve Tissue; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Siderophores; Transferrin