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Results for “Flocculation Tests”

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At least 667 records · Page 37Linked to original sources
PubMed2001

Flocculation/flotation/ultrafiltration integrated process for the treatment of cork processing wastewaters.

Membrane fouling is the major problem in the treatment by ultrafiltration (UF) of the cork processing wastewaters. This problem leads to drastic reduction on the permeate fluxes and has been associated with wastewaters phenolic/tannic colloidal matter. The present work proposes a flocculation/flotation/ultrafiltration integrated process for the treatment of these wastewaters. A flocculation study was carried out in jar-test equipment with chitosan. The zeta-potential and the particle size were monitored at different pH values and for different chitosan concentrations. The results showed an increase of the zeta-potential when chitosan is added and a significant increase of the effluent particle size with the decrease of the pH. A dissolved-air flotation study was performed with the flocculated wastewater. The parameters varied were the operating pressure and the recycle ratio. It was observed that for higher pressures and at a recycle ratio of 0.19 the polyphenols removal was higher. The UF experiments were carried out in flat-sheet cells of 13.2 cm2 of membrane surface area at transmembrane pressures of 1-3 bar. A commercial membrane (Ropur-TS60) and four cellulose acetate membranes with molecular weight cutoff (MWCO) ranging from 4.5 to 86 kDa were used. The flocculation/flotation pretreatment led to the enhancement of the UF permeate fluxes. For the membrane with higher MWCO, the permeate flux enhancement reached 130%.

Algorithms↗
PubMed2001

Collision efficiency factor of bubble and particle (alpha bp) in DAF: theory and experimental verification.

The collision efficiency factor of bubble and particle (alpha bp) in dissolved air flotation (DAF) can be calculated theoretically by trajectory analysis, which takes into account both hydrodynamics and interparticle forces. To determine the theoretically optimum particle size for any given bubble size, a collision efficiency diagram for DAF was developed where collision efficiency is contoured on a plane of particle and bubble sizes for different conditions of particle zeta potential. A set of experiments tested the validity of the suggested collision efficiency diagram, and examined whether pretreatment is important and why slight coagulant overdosing and shorter flocculation times are generally preferred in DAF, both current accepted practice. Batch DAF reactors were used and kaolin samples were prepared from jar tests using different alum dosages and flocculation times. The particle size distribution, particle zeta potential, and turbidity removal in each experiment were measured, as were bubble size and zeta potential. The results agreed well with the predictions of the collision efficiency diagram and explained current practices. A collision efficiency diagram identifies the pretreatment goal, i.e., tailoring of the optimum characteristics required of particles (zeta potential and size) under existing operational bubble characteristic.

Air↗
PubMed2006

Gamma radiation-induced grafting of a cationic monomer onto chitosan as a flocculant.

Grafting of (2-methacryloyloxyethyl) trimethyl ammonium chloride onto chitosan through gamma-radiation in acidic aqueous solutions was achieved for production of a novel flocculant. The grafted copolymer was characterized by Fourier-transform infrared, X-ray powder diffraction and thermogravimetric analysis. The effects of reaction parameters, such as total absorbed dose, dose rate, monomer concentration and temperature, on grafting percentage were investigated. The flocculation capacities of the grafted copolymer were evaluated with 0.25% (w/v) kaolin suspensions using the standard jar test. The results demonstrate the superiority of the grafted copolymer over chitosan as a flocculant.

Cations↗
PubMed1999

Ethanol production by a flocculant yeast strain in a CSTR type fermentor with cell recycling.

Tests were performed in a continuous stirred tank reactor (CSTR), with and without cell recycling, to produce ethanol. The reactor without cell recycling produced the kinetic model of ethanol production, whereas the reactor with cell recycling allowed for a study of process stability. The Levenspiel kinetic model was adopted; however, in the case of fermentation with cell recycling, the coefficient of cell death was added. It was observed that cellular viability varied greatly throughout the fermenting process and that microaeration is of fundamental importance in maintaining the stability of the process.

Journal Article↗
PubMed1994

An effective toxoid from tetanus toxin prepared by stepwise iodination of purified toxin.

Purified samples of tetanus toxin were gradually iodinated by stepwise addition of iodine, up to saturation. The residual capacity of each sample to provoke tetanus was tested by injecting sc 25 Lf (Limit of flocculation) in mice. Toxicity diminished in relation to iodine incorporated, and with iodine-saturated samples, doses of up to 100 Lf in mice, or 500 Lf in guinea-pigs, proved innocuous. Mice immunized with two doses of this toxoid adsorbed on Al(OH)3, and challenged with standard lethal toxin, gained protection against 10 MLD (Minimum Lethal Doses). Guinea-pigs were immunized by a single sc dose of 27.5 Lf with fluid toxoid, and all resisted challenge against 10 MLD applied 30 days later. The mice sera gave strong immunoprecipitation lines against the native toxin. The findings indicated that by controlled iodination of tetanus toxin an effective and inexpensive toxoid can be prepared.

Animals↗
PubMed1993

Yeast flocculation: lectin synthesis and activation.

Yeast flocculation involves binding of surface lectins to carbohydrate receptors on neighbouring cell walls. Brewing strains of Saccharomyces cerevisiae normally become flocculent in the stationary phase of growth. This paper presents evidence that lectins are synthesized in exponential phase, inserted into the cell wall, and activated later at the time of flocculation onset. Cycloheximide failed to prevent flocculation unless it was added in early growth; with later additions progressively larger degrees of flocculation occurred. Flocculation onset was delayed by cycloheximide but was otherwise cycloheximide insensitive. Preflocculent cells could be artificially activated to full flocculation by heat. Artificial activation of samples from growing yeast cultures confirmed the progressive synthesis of lectins throughout exponential growth. Pronase E treatment of whole cells prior to heating prevented any activation of flocculation. It was concluded that lectins were synthesized continuously from an early stage of growth and rapidly inserted into the cell wall (accessible by pronase E), where they remained inactive for up to 14 h, before being activated at flocculation onset by an as-yet unknown mechanism. It was found that lectin synthesis and activation occurred in all brewing strains tested.

Beer↗
PubMed2006

Occurrence of Giardia and Cryptosporidium in water supplies of Russia and Bulgaria.

The aim of the present study was to investigate water supplies in southern Russia and Bulgaria, in order to estimate the occurrence of Giardia and Cryptosporidium in drinking water resources from these countries. A total of 166 water samples of different origin (surface, tap, bottled, well, spring and waste water) were collected from Rostov (southern Russia), Sofia and Varna (Bulgaria) Greater Areas and screened for the detection of Giardia cysts and Cryptosporidium oocysts. The method incorporated concentration of water samples by filtration and flocculation, sucrose purification, (oo)cyst detection/identification by immunofluorescence test and differential interference contrast. Sixteen out of 166 samples (9.6%) were positive for Giardia and 30 (18.1%) positive for Cryptosporidium. Both Giardia and Cryptosporidium were detected in tap, river, well and waste waters. Giardia cysts were additionally detected in bottled water. Particularly some river, waste and well water samples were highly contaminated with (oo)cysts. This study has shown that drinking water supplies in Russia and Bulgaria are subject to contamination with Giardia and Cryptosporidium, with potential hazards for the public health.

Animals↗
PubMed2001

Solar oxidation and removal of arsenic at circumneutral pH in iron containing waters.

An estimated 30-50 million people in Bangladesh consume groundwater with arsenic contents far above accepted limits. A better understanding of arsenic redox kinetics and simple water treatment procedures are urgently needed. We have studied thermal and photochemical As(III) oxidation in the laboratory, on a time scale of hours, in water containing 500 micrograms/L As(III), 0.06-5 mg/L Fe(II,III), and 4-6 mM bicarbonate at pH 6.5-8.0. As(V) was measured colorimetrically, and As(III) and As(tot) were measured by As(III)/As(tot)-specific hydride-generation AAS. Dissolved oxygen and micromolar hydrogen peroxide did not oxidize As(III) on a time scale of hours. As(III) was partly oxidized in the dark by addition of Fe(II) to aerated water, presumably by reactive intermediates formed in the reduction of oxygen by Fe(II). In solutions containing 0.06-5 mg/L Fe(II,III), over 90% of As(III) could be oxidized photochemically within 2-3 h by illumination with 90 W/m2 UV-A light. Citrate, by forming Fe(III) citrate complexes that are photolyzed with high quantum yields, strongly accelerated As(III) oxidation. The photoproduct of citrate (3-oxoglutaric acid) induced rapid flocculation and precipitation of Fe(III). In laboratory tests, 80-90% of total arsenic was removed after addition of 50 microM citrate or 100-200 microL (4-8 drops) of lemon juice/L, illumination for 2-3 h, and precipitation. The same procedure was able to remove 45-78% of total arsenic in first field trials in Bangladesh.

Arsenic↗
PubMed1997

Cryptosporidium parvum in environmental samples in the Sligo area, Republic of Ireland: a preliminary report.

To detect Cryptosporidium in environmental specimens in the Republic of Ireland, grab samples of river water were prepared by calcium carbonate flocculation, and marine mussel tissue homogenated prior to testing with a fluorescently labelled monoclonal antibody and fluorescence microscopy. The parasite was detected in both river waters and marine mussels (Mytilus edulis). Filter feeders such as Mytilus edulis may be of value as biological monitors for the presence of cryptosporidial oocysts in sea water. The presence of Cryptosporidium in river and marine waters and, in particular, contaminating mussels used for human consumption, has obvious health implications.

Animals↗
PubMed2003

Effect of physiological media on the stability of surface-adsorbed DNA-dendron-gold nanoparticles.

Plasmid DNA was adsorbed onto 87-nm gold nanoparticles to which were adsorbed a layer of novel cationic dendrons. The behaviour of this DNA-dendron-gold system in cell culture media has been described. Adsorption onto the gold nanoparticles of lipophilic cationic dendrons, with either 8 [(C12)(3)Lys7(NH2)(8)] or 16 [(C12)(3)Lys15(NH2)(16)] free amino groups on their outer surfaces and incorporating a nuclear localization signal peptide (NLS), resulted in positively charged nanoparticles with a corresponding small increase in particle size. Evidence suggested that the interaction between the gold nanoparticles and the dendron was mediated by hydrophobic forces. With an increase in ionic strength, the apparent particle size of the dendron-stabilized-gold particles increased, but at higher salt concentrations than plain gold sols. Addition of plasmid DNA did not markedly reduce the surface potential of the dendron-gold complex but resulted in an approximately 10-20% increase in hydro-dynamic diameter. Increasing ionic strength increased the apparent size of the DNA-dendron-gold particles, up to a maximum diameter of approximately 900 nm. Importantly, in cell culture media the size of the DNA-dendron-gold nanoparticles increased markedly, as surface potential was reduced. The presence of serum components partially ameliorated these effects, possibly due to steric stabilization of the particles. Release of the DNA from the complex was compromised in cell culture media (compared with water). This, coupled with the flocculation of the carrier, demonstrated the importance of testing delivery systems in the presence of relevant physiologically based fluids before cell culture or in-vivo studies.

Adsorption↗