SEARCH · PubMed Health

Results for “Flocculation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources

PubMed2003

Culture conditions for flocculant production by Paenibacillus polymyxa BY-28.

A new flocculant-producing bacterium Paenibacillus polymyxa BY-28 was isolated from soil. The optimal culture media for flocculant production were 2% glucose, 0.3% KH2PO4, 0.1% bean cake powder, 0.05% CaC12 and 0.05% (w/v) MgSO4.7H2O. Optimal culture temperature was 30 degrees C and pH was 6-8. Flocculants produced under optimal conditions efficiently aggregated various organic and inorganic suspensions in simulated water as well as in wastewater by addition of bivalent and trivalent cations Ca2+. From Zeta-potential measurement, the dominant role of microbial flocculant in the flocculation process is based on the bridging mechanism, and the role of CaCl2 is to decrease the negative electrical charge of the Kaolin clay particles.

Aluminum Silicates↗

PubMed1985

Discrimination by heat and proteinase treatments between flocculent phenotypes conferred on Saccharomyces cerevisiae by the genes FLO1 and FLO5.

The effects of elevated temperature and of digestion with a variety of proteinases on the flocforming ability of flocculent strains of Saccharomyces cerevisiae, both genetically defined (FLO1 and FLO5) laboratory and genetically undefined brewing strains, have been determined. This has permitted classification of the flocculent phenotypes of these strains according to criteria other than quantitative grading of flocculence. The flocculent phenotypes conferred by both the FLO1 and the FLO5 gene were irreversibly lost upon treatment with pronase, proteinase K, trypsin or 2-mercaptoethanol treatments. However, the floc-forming ability of cells of the FLO1 strain ABXL-1D was destroyed by chymotrypsin digestion and was stable to incubation at 70 degrees C, whereas the floc-forming ability of cells of the FLO5 strain ABXR-11A was resistant to the action of chymotrypsin and was heat labile. Tetrad analysis of a cross of these FLO1 and FLO5 strains indicated that the chymotrypsin and heat sensitivity phenotypes were FLO-gene determined. It appears that expression of the FLO1 and FLO5 genes leads to the production of different and characteristic cell-wall proteins underlying their respective flocculent phenotypes.

Chymotrypsin↗

PubMed1999

Cell surface galactosylation is essential for nonsexual flocculation in Schizosaccharomyces pombe.

We have isolated fission yeast mutants that constitutively flocculate upon growth in liquid media. One of these mutants, the gsf1 mutant, was found to cause dominant, nonsexual, and calcium-dependent aggregation of cells into flocs. Its flocculation was inhibited by the addition of galactose but was not affected by the addition of mannose or glucose, unlike Saccharomyces cerevisiae FLO mutants. The gsf1 mutant coflocculated with Schizosaccharomyces pombe wild-type cells, while no coflocculation was found with galactose-deficient (gms1Delta) cells. Moreover, flocculation of the gsf1 mutant was also inhibited by addition of cell wall galactomannan from wild-type cells but not from gms1Delta cells. These results suggested that galactose residues in the cell wall glycoproteins may be receptors of gsf1-mediated flocculation, and therefore cell surface galactosylation is required for nonsexual flocculation in S. pombe.

Carbohydrates↗

PubMed1979

Changes in electrophoretic mobility and lytic enzyme activity associated with development of flocculating ability in Saccharomyces cerevisiae.

Cells from stationary-phase cultures of two strains of Saccharomyces cerevisiae (3 and 20) failed to flocculate when grown in a complex or a chemically defined medium, while those of two other strains (11 and 13) flocculated when grown in either medium. Strain 30 flocculated when grown in complex but not defined medium and harvested from stationary-phase cultures. pH-electrophoretic mobility measurements on all five strains showed that mobility attributable to carboxyl groups usually increased as cultures progressed from the exponential to the stationary phase, while that caused by phosphate groups tended to decline. Acquisition of flocculating ability was accompanied in strains 11 and 30 by a slight increase in amidase activity, and greater increases compared with nonflocculent populations in activities of leucine aminopeptidase. alpha-mannosidase, and proteinase C. Activities of proteinases A and B showed no correlation with acquisition of flocculating ability.

Amidohydrolases↗

PubMed2005

Flocculation control study based on fractal theory.

A study on flocculation control based on fractal theory was carried out. Optimization test of chemical coagulant dosage confirmed that the fractal dimension could reflect the flocculation degree and settling characteristics of aggregates and the good correlation with the turbidity of settled effluent. So that the fractal dimension can be used as the major parameter for flocculation system control and achieve self-acting adjustment of chemical coagulant dosage. The fractal dimension flocculation control system was used for further study carried out on the effects of various flocculation parameters, among which are the dependency relationship among aggregates fractal dimension, chemical coagulant dosage, and turbidity of settled effluent under the conditions of variable water quality and quantity. And basic experimental data were obtained for establishing the chemical coagulant dosage control model mainly based on aggregates fractal dimension.

Aluminum Hydroxide↗

PubMed2006

Influence of chitosan characteristics and environmental conditions on flocculation of anaerobic sludge.

The effects of chitosan characteristics (i.e., degree of deacetylation [DD] and molecular weight) and environmental conditions (i.e., ionic strength and pH) on the flocculation of anaerobic sludge were investigated. The results showed that chitosan enhanced the flocculation of sludge, and the flocculation efficiency depended on both the degree of deacetylation and molecular weight. Chitosan with 85%DD was more effective than that with 70%DD, as the former required a lower dose to obtain 90% flocculation at all studied pH values. In addition, low molecular weight chitosan enhanced the flocculation better than high molecular weight chitosan. The increase in ionic strength (up to 0.1 M) of the suspension helped reduce restabilization that occurred when chitosan was overdosed. In general, chitosan has potential to be used as an effective cationic bioflocculant, which is able to function either in acidic or neutral conditions, and very small amounts of chitosan (less than 4 mg/g dried sludge) are required.

Anaerobiosis↗

PubMed2001

[Effective factors of flocculation-DAF pilot process treating water with low temperature and low turbidity from Miyun reservoir].

The hydraulic parameters in coagulation, flocculation and flotation units of DAF pilot process were systematically investigated when employing flocculants AS and PAC respectively. In general, the available parameters for PAC are more favorable in DAF process. For PAC as a flocculant during DAF run, the favorable coagulation rapid mixing time is 15 s, the flocculant mixing time is no less than 5 minutes. However for AS, the corresponding time values are greater than 30 s and more than 7.5 minutes respectively. The available coagulation mixing intensity is 300-1000 s-1. The available flocculation mixing intensity (average G) is 40-140 s-1, and the GT (average) value is greater than 2 x 10(4). Both equal-speed mixing and two or three stages mixing could provide slight better turbidity removal. For MJ model nozzle, the suitable recycle ratio is 5.0%-8.3% at dispersed pressure of 2.5-3.3 kg.cm2. The detention time and hydraulic intensity in contact zone of DAF tank have important effects on DAF turbidity removal.

Flocculation↗

PubMed2001

Pretreatment of bakery wastewater by coagulation-flocculation and dissolved air flotation.

The pretreatment of wastewater from a large-scale bakery was studied. In the coagulation-flocculation reaction, it was found that both alum and FeCl3 were effective in the jar tests. When at coagulant dosage of 90 to 100 mg/l, 55% of COD and 95 to 100% of SS could be removed. The optimum pH was at 6.0. In addition, the removal of SS was affected by pH more significantly, while the removal of COD was not affected in the pH range of 6.0 to 8.0. In the DAF experiments, 48.6% of COD and 69.8% of SS were removed in 10 min at a pressure of 4 kg/cm2, recycle ratio of 0.3 l/min, and pH of 6.0. Upon the addition of 100 mg/l of alum, the removal efficiency of COD did not increase while SS removal increased to 82.1%. It was found that 5-min flocculation time did improve the COD removal while it had little effect on SS removal. Flocculation for longer than 5 min did not enhance the flotation performance. Similar phenomena were observed when FeCl3 was used as the coagulant, except that flocculation had an insignificant effect on COD and SS removal. It was also found that FeCl3 was relatively more effective than alum. In summary, both coagulation-flocculation and DAF were efficient for the pretreatment. The advantages and disadvantages were discussed.

Air↗

PubMed2001

Activated sludge flocculation: direct determination of the effect of calcium ions.

The effect of calcium on activated sludge flocculation dynamics is investigated using a unique experimental technique. The technique allows on-line analysis of the size of activated sludge flocs during flocculation and provides valuable insight into the mechanisms of flocculation. Activated sludge samples were firstly sonicated for 3 minutes at 50 W and then stirred at 100 rpm. The floc size was subsequently measured on-line using a Malvern Mastersizer/E. For concentrations of calcium less than 4 meq/L no significant increase in final floc size was observed even though an increase in the initial rate of change of floc size could be seen. Addition of calcium greater than 4 meq/L resulted in a dramatic increase in floc size. Results from this investigation support the theory that cations are involved in flocculation through cationic bridging, and will be used in ongoing investigations to model the flocculation process.

Calcium Chloride↗

PubMed2003

Fenton's reagent and coagulation-flocculation as pretreatments of combined wastewater for reuse.

In Mexico City, drinking water is mainly produced from groundwater (70%). This practice has caused collateral problems such as Mexico City's soil sinking (5-30 cm/year). One of the most viable alternatives to palliate this problem is the treatment of wastewater for reuse in either irrigation or for groundwater artificial recharge. This paper presents the evaluation of two physicochemical pretreatment systems to treat the wastewater from the metropolitan area of the Mexican Valley that are conducted by two main sewage systems called Great Canal and Churubusco River. In this research two treatment processes were studied: 1) coagulation-flocculation and, 2) Fenton's reagent. For each one of these processes suggested, tests were performed with wastewater samples of the Great Canal and the Churubusco River mixed in a volume ratio of 1:1. In the case of the coagulation-flocculation process, additional experiments were performed to determine the optimal conditions by applying an experimental design technique. In this experimental design, six coagulant agents were considered (alum, ferric chloride, three coagulant reagents of polymeric kind with aluminium and a coagulant reagent of natural origin), and three flocculant agents (an anionic, a cationic, and a non ionic polymers). Concerning the application of the Fenton's reagent (Fe2+:H2O2), the experimental variables were the weight ratio of the ferrous iron and the hydrogen peroxide and the concentrations of these reagents. The pH value was controlled to be near to 4. For the best experimental conditions, the effluent of the Fenton's method showed similar physicochemical characteristics to the wastewater treated by coagulation-flocculation. Nevertheless, Fenton's reagent showed two very important advantages compared to the coagulation-flocculation process: a disinfecting effect and a lower production of residual sludges.

Cities↗

PubMed2003

Relationship between flocculation of activated sludge and composition of extracellular polymeric substances.

Activated sludge flocs are a flocculated mass of microorganisms, extracellular polymeric substances (EPS) and adsorbed organic and inorganic material. The structure of the floc is very heterogeneous and flocs with very different properties and morphologies may occur, depending on the conditions in the activated sludge treatment plant and wastewater composition. Present thinking suggest that cations, such as calcium, create cationic bridges with EPS excreted by the bacteria and thereby hold the various floc constituents together. However, due to the complex and heterogeneous nature of activated sludge, the mechanisms have neither been thoroughly investigated nor successfully quantified. A better understanding and description of the biological flocculation process is necessary in order to establish more efficient operational strategies. The main aim of this study was to get a comprehensive and unique insight into the floc properties of activated sludge and to assess the relative impact of chemical and physical parameters. A variety of sludges from full scale treatment plants with different settling properties were characterised. The interrelationships between floc parameters such as composition of EPS, surface properties and floc structure, and their effect on the flocculation and separation properties were assessed. The results indicate that the EPS, both in terms of quantity and quality, are very important for the floc properties of the activated sludge. However, presence of filaments may alter the physical properties of the flocs considerably. The EPS showed positive correlations to sludge volume index (SVI) if only sludges with low or moderate numbers of filaments were included. The surface properties were more affected by the composition of the EPS than by the number of filaments. The EPS showed positive correlation to negative surface charge and a negative correlation to relative hydrophobicity and flocculation ability. The negative correlation between flocculation ability and amount of EPS was surprising. The shear sensitivity, measured as degree of erosion of flocs when subjected to shear, was more affected by floc size and number of filaments than amount of EPS.

Bacteria↗

PubMed2003

Application of organic polymeric flocculants in centrifugal dewatering of oil refinery sludge.

In order to evaluate the applicability of the organic polymeric flocculants (OPF) in the treatment of oil refinery sludge, experiments were conducted to show that OPF have better performance of flocculation than inorganic flocculants. Both the anionic and cationic OPF have satisfactory flocculation efficiency in oil sludge treatment, but the latter are more cost-efficient. Among the over 20 types of flocculants tested, 2 OPF (CPAM-2 and HPAM-2) were selected as the treatment agents, based on their good treatment performances, oil-resistance and economic feasibility. It was demonstrated in the industrial-scale centrifugal dewatering experiments that the application of either CPAM-2 or HPAM-2 could achieve high treatment efficiency of the oil sludge dewatering and reduce the COD of centrifugal liquid to less than 1000 mg/L.

Accidents↗

PubMed2006

[Atomic force microscope analysis of adsorption and flocculation behaviors of polydiallyldimethylammonium salts: influence of counterion].

High molecular weight polydiallyldimethylammonium nitrate (PDADMANO3) and polydiallyldimethylammonium sulfate (PDADMASO4) were prepared from polydiallyldimethylammonium chloride (PDADMAC). The effects of univalent counterions (Cl-, ON3-) and bivalent counterion (SO4(2-) on solution, absorption and flocculation properties of polydiallyldimethylammonium salts (PDADMAX) were investigated by conductivity, reduced viscosity, atomic force microscopy (AFM), residual turbidity, distributions of zeta potential and flocculation index of kaolin suspension. The results show that different counterions possess significant effects on solution properties, absorption and flocculation behaviors of PDADMAX. PDADMANO3 shows stronger flocculation efficiency and "neutralization action", whereas PDADMASO4 shows the wider optimum dosage and larger floc size, as well as "bridging action". In particular, AFM image of single polyelectrolyte polymer is a valuable tool for the analysis of the absorption and flocculation mechanism of polyelectrolye.

Adsorption↗

PubMed1997

Constitutive flocculation in Saccharomyces cerevisiae through overexpression of the GTS1 gene, coding for a 'Glo'-type Zn-finger-containing protein.

The product of the cloned GTS1 gene is characterized by structural features found in transcription factors. It contains one Zn-finger motif (CXXCX16CXXC) situated in the N-terminal end with a high degree of homology to the newly identified 'Glo' family of Zn-finger proteins (Ireland et al., 1994, EMBO J. 13, 3812-3821). The C-terminal end of the protein is characterized by poly (Ala-Gln) and poly-Gln stretches. Poly-Gln are part of trans-acting motifs in known transcription factors. Overexpression of the GTS1 gene results in constitutive flocculation. Whole cell electrophoretic mobility and hydrophobicity of GTS1 overexpressing cells was respectively lower and higher relative to control cells. GTS1-induced flocculation is hardly sensitive to mannose in contrast to FLO1-determined flocculation. Overexpression of the GTS1 gene in a flo1 background does not abolish flocculation, suggesting that the FLO1 gene is not linked with the GTS1 gene in a 'flocculation pathway'.

Amino Acid Sequence↗

PubMed1998

Modeling brewers' yeast flocculation

Flocculation of yeast cells occurs during the fermentation of beer. Partway through the fermentation the cells become flocculent and start to form flocs. If the environmental conditions, such as medium composition and fluid velocities in the tank, are optimal, the flocs will grow in size large enough to settle. After settling of the main part of the yeast the green beer is left, containing only a small amount of yeast necessary for rest conversions during the next process step, the lagering. The physical process of flocculation is a dynamic equilibrium of floc formation and floc breakup resulting in a bimodal size distribution containing single cells and flocs. The floc size distribution and the single cell amount were measured under the different conditions that occur during full scale fermentation. Influences on flocculation such as floc strength, specific power input, and total number of yeast cells in suspension were studied. A flocculation model was developed, and the measured data used for validation. Yeast floc formation can be described with the collision theory assuming a constant collision efficiency. The breakup of flocs appears to occur mainly via two mechanisms, the splitting of flocs and the erosion of yeast cells from the floc surface. The splitting rate determines the average floc size and the erosion rate determines the number of single cells. Regarding the size of the flocs with respect to the scale of turbulence, only the viscous subrange needs to be considered. With the model, the floc size distribution and the number of single cells can be predicted at a certain point during the fermentation. For this, the bond strength between the cells, the fractal dimension of the yeast, the specific power input in the tank and the number of yeast cells that are in suspension in the tank have to be known. Copyright 1998 John Wiley & Sons, Inc.

Journal Article↗

PubMed1993

Physical localization of the flocculation gene FLO1 on chromosome I of Saccharomyces cerevisiae.

The genetics of flocculation in the yeast Saccharomyces cerevisiae are poorly understood despite the importance of this property for strains used in industry. To be able to study the regulation of flocculation in yeast, one of the genes involved, FLO1, has been partially cloned. The identity of the gene was confirmed by the non-flocculent phenotype of cells in which the C-terminal part of the gene had been replaced by the URA3 gene. Southern blots and genetic crosses showed that the URA3 gene had integrated at the expected position on chromosome I. A region of approximately 2 kb in the middle of the FLO1 gene was consistently deleted during propagation in Escherichia coli and could not be isolated. Plasmids containing the incomplete gene, however, were still able to cause weak flocculation in a non-flocculent strain. The 3' end of the FLO1 gene was localized at approximately 24 kb from the right end of chromosome I, 20 kb centromere-proximal to PHO11. Most of the newly isolated chromosome I sequences also hybridized to chromosome VIII DNA, thus extending the homology between the right end of chromosome I and chromosome VIII to approximately 28 kb.

Chromosome Mapping↗

PubMed1998

Ultrasonic Spectroscopy Study of Flocculation and Shear-Induced Floc Disruption in Oil-in-Water Emulsions.

Ultrasonic attenuation spectroscopy was used to study flocculation and shear-induced disruption of flocs in oil-in-water emulsions. The ultrasonic attenuation spectra (1 to 150 MHz) of a series of 10 wt% corn oil-in-water emulsions (r32 = 0.2 µm) were measured. Depletion flocculation was induced in the emulsions by adding different concentrations (0 to 0.2 wt%) of a nonadsorbing biopolymer (xanthan) to the aqueous phase. At low frequencies, the attenuation coefficient of the emulsions decreased with increasing flocculation due to overlap of the thermal waves generated by the droplets. These observations were in good agreement with a theory recently developed to account for the influence of droplet flocculation on the ultrasonic properties of emulsions. The ultrasonic technique was also used to monitor the breakdown of flocs under shear flow. The dependence of the ultrasonic properties of emulsions on flocculation means that ultrasonic attenuation spectroscopy can be used to study droplet interactions in concentrated emulsions. Copyright 1998 Academic Press.

Journal Article↗

PubMed1998

Shear-Induced Flocculation of Colloidal Particles in Stirred Tanks.

Colloidal polystyrene and paramagnetic particles consisting of mixtures of polystyrene and magnetite are used to experimentally investigate flocculation kinetics in a stirred tank under turbulent shear flow. The effects of various parameters-agitation speed, solution pH, ionic strength, particle size, and particle concentration-on the flocculation rate are investigated. A trajectory model applicable for shear-flow systems is formulated to describe particle flocculation in stirred tanks. The collision efficiency of particles is obtained from the limiting trajectory of one particle moving toward another and is a function of interparticle forces and flow properties. The collision frequency is determined as a function of particle size and energy dissipation. The flocculation frequency is then determined by multiplying the collision frequency by the collision efficiency and is incorporated into a population balance model to predict the particle size evolution. Results suggest that the flocculation rate is enhanced by increasing the agitation speed, even though the collision efficiency is decreased at a higher agitation speed. It is also found that the collision rate increases and the collision efficiency decreases as the particle size ratio is increased. Results also suggest that the breakup rate of aggregates in a turbulent shear flow could be significant and may need to be included in the population balance modeling to correctly predict the evolution of particle size distribution. Copyright 1998 Academic Press.

Journal Article↗