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At least 397 records · Page 22Linked to original sources

PubMed2000

[Spectrophotometric determination of trace cadmium in polyferric sulphate flocculent].

A new sensitive method for determining trace cadmium in polyferric sulphate flocculent is proposed in the paper. The new sensitive method is spectrophotometric method. The color reagents are the butylrhodamin B and potassium iodide. The surfactant is the polyvingl alcohol(PVA). The maximum absorbency wavelength is 607 nm. The molar absorptivity is 4.99 x 10(5) L.mol-1.cm-1. The sandell sensitivity is 2.25 x 10(-4) micrograms Cd2+.cm-2. The Beer's law is obeyed for Cd(II) in the range of 0-1.5 micrograms.25 mL-1. The recovery is 96%-105% and the sample processing procedure is simple. This method has been applied to determination of trace Cd(II) in polyferric sulphate flocculent. The determining results are satisfactory.

Cadmium↗

PubMed2003

Influence of flocculation conditions in the performance of an experimental domestic sewage treatment plant consisting of an anaerobic expanded bed reactor followed by dissolved air flotation.

This paper presents the results of a study performed with an experimental domestic sewage treatment plant (240 m3 x d(-1) flow) consisting of expanded bed anaerobic reactor (EBAR) followed by dissolved air flotation (DAF) unit. For the flotation step, the anaerobic reactor effluent was previously coagulated with 50 mgFeCl3 x l(-1) and flocculated under different conditions (mean velocity gradient, Gf, and flocculation time, Tf). The Gf values were from 60 to 100 s(-1) associated with 13 and 20 min Tf values. During the tests, the following operational conditions of the flotation unit were maintained: chemical addition (50 mgFeCl3 x l(-1)), 18% recirculation rate associated with a pressure of 450 +/- 10 kPa in the saturation chamber and overflow rate of 180 m3 x m(-2) x d(-1). Temperature ranged from 23.8 degrees C to 30.0 degrees C. Best results were achieved for Gf = 80 s(-1) and Tf = 20 min. For these conditions, the DAF unit removal efficiencies were: 94.4% for chemical oxygen demand (with 53 mg x l(-1) COD residual), 87% for phosphorus (with 0.80 mgP x l(-1) residual), 96.7% for total suspended solids (with 9 mg x l(-1) TSS residual) and 96.4% for turbidity (with 12.9 NTU residual), when the anaerobic reactor effluents have worst quality during the whole day.

Air↗

PubMed2004

Mass transfer impacts in flocculent and granular biomass from SBR systems.

An experimental study was conducted to describe mass transfer impacts within nitrifying aggregates sourced from sequencing batch reactor (SBR) activated sludge systems. Flocculent and granular sludge with high nitrification activity was obtained in two laboratory SBR systems, supplied with a synthetic, ammonium-based feed. The flocculent biomass was fractionated using a sieving procedure, in order to obtain biomass fractions with different particle size distributions. The oxygen uptake rate (OUR) response to changes in dissolved oxygen concentration was measured under highly controlled conditions in a titrimetric and off-gas analysis (TOGA) sensor, and the results used to assess mass transfer effects. As the average particle size of the biomass increased, mass transfer limitations were found to increase significantly. Empirically fitted, apparent K(S,O2) values were demonstrated to be highly dependent on particle size, and reflect the mass transfer limitations occurring in the aggregates within a given system. Such parameters thus have little to do with the actual biokinetic parameter from which they are derived. The results obtained from the TOGA sensor study were consistent with those obtained from a microelectrode study on the same nitrifying granules. Together, these studies add considerable weight to the conclusion that consideration of external and internal mass transfer limitations is vital to the accurate description of activated sludge treatment processes, particularly those with a high oxygen uptake rate.

Biomass↗

PubMed2004

[Flocculation and removal of water bloom cells Microcystis aeruginosa by chitosan-modified clays].

The kinetics of flocculation and removal of Microcystis aeruginosa by chitosan-modified clays was studied. The efficiency of flocculating and removing of algal cells was greatly improved after the modification of the clays. About 80% of algae cell was removed in 0.5 hour, and 90% in 2 hours, when 11 mg/L modified sepiolite was added. Algae-removal capacities of different clays were all improved to a similar level of >90% at a total loading of 11 mg/L after being modified with chitosan. The efficiency of algae-removing was reduced when the clay loading was larger or smaller than the optimum loading.

Aluminum Silicates↗

PubMed2005

[Continuous ethanol fermentation using self-flocculating yeast in multi-stage suspended bioreactors coupled with directly recycling of waste distillage].

A fermentation system composed of four airlift suspended-bed bioreactors in series and with a total working volume of 4800 mL was established. Continuous ethanol fermentation using self-flocculating yeast SPSC01, a fusant from Saccharomyces cerevisiae and Schizosaccharomyces pombe, and two-stage enzymatic hydrolyte of dry milling corn powder, was continuously run for 120 days. All of the backset distillage collected after distilling the final beer was used to mix the corn powder and no any other wastes except the solid residue of corn powder was discharged from the fermentation system, which guaranteed the distillage to be recycled at its maximum. The experimental results revealed that both ethanol and residual sugar in the final beer could be maintained relatively stable with their average levels of 93.6 and 7.9 g/L, respectively when the fermentation system was operated at the dilution rate of 0.05 h(-1). Parameter oscillations reported previously were also observed for the first and second bioreactors, but were effectively attenuated thereafter, which indicated that high yeast cell concentrations resulted from the self-immobilization of this special self-flocculating strain contributed to damp these oscillations. The monitoring of residual nitrogen and phosphor indicated that the accumulations of these nutritional elements occurred and the amount of these inorganic salts supplemented in the substrate should be decreased properly.

Bioreactors↗

PubMed2003

[Breeding of excellent baker's yeast strain with good flocculation].

An excellent baker's yeast strain ZLTH-58 (MATa/alpha, leu-, FLO1) with high biomass, high-sugar-tolerance and good flocculation was constructed by primary screening, isolation of haploid, mutagenesis, cloning and expression of FLO1 gene and hybridization. The results showed that strain ZLTH-58 had excellent properties of the parental strains BL56 and BL61. The biomass of strain ZLTH-58 was 1.21 times of the parental strain BL56; The ability of high-sugar-tolerance of strain ZLTH-58 was higher than the parental strain BL61. The ability of flocculation of strain ZLTH-58 was better than the parental strains BL56 and BL61. The factors that affected the biomass of strain ZLTH-58 were also detected. Biomass reached 83.06 g/L under the optimal fermentation conditions, having a 1.35-fold improvement. Strain ZLTH-58 is also stable in genetics characters by analysis of genetic stability and it has the potential for use in industrial processes.

Biomass↗

PubMed1978

[About the importance of chemical flocculation of wastewater in regard to hygienical aspects (microbiological and virological examinations in a wastewater treatment plant) (author's transl)].

In a small wastewater treatment plant corresponding samples from the intake and outtake of the chemical flocculation were chemically, microbiologically and virologically investigated and compared. It was found that both, the plate count and the number of coliforms, decreased about 90% to 95%. The phosphate content went down about 88%. The BOD5 reduction was ca. 80%, the COD reduction ca. 50%. Poliomyelitisviruses were found regularly in the intake but never in the outtake. Specially in regard to the high plate count- and virusreduction the chemical flocculation seems to be remarkable from the hygienical point of view not only for limnic but also for coastal waters.

Escherichia coli↗

PubMedDate not supplied

The influence of charged lipids on the flocculation and coalescence of oil-in-water emulsions. II: Electrophoretic properties and monolayer film studies.

The influence of calcium ions on the electrophoretic properties of phospholipid stabilized emulsions containing various quantities of the sodium salts of oleic acid (SO), phosphatidic acid (SPA), phosphatidylinositol (SPI), and phosphatidylserine (SPS) was examined. The critical flocculation concentration of calcium corresponded to a critical zeta potential in all but one of the systems. Systems of approximately equal zeta potential in 0 mM Ca++ had different zeta potentials in dilute solutions of Ca++. A comparison of emulsions of similar polydispersity suggests that these differences may be largely related to differences in particle size and surface area of the emulsions. The influence of Ca++ on the monolayer properties of mixed films containing phosphatidylcholine (PC) with either SPA or SO was also examined at the air-water interface. Films containing PC with SPA were more expanded on a subphase containing calcium compared to a subphase with no calcium. In addition, the compression of films containing PC with SO demonstrated two collapse pressures while SPA was relatively more miscible in the film. This suggests that phase separation of interfacial lipids occurs more easily in systems containing PC and SO. These results may help to explain differences in the flocculation and coalescence of emulsions stabilized by lipid films of different composition.

Electrophoresis↗

PubMed1989

Continuous fermentation with yeast (Shizosaccharomyces pombe) floccules for ethanol production.

This paper describes an experimental study of continuous fermentation of saccharified starch solution to produce ethanol with yeast particles of a highly flocculent strain of Schizosaccharomyces pombe, which were treated as immobilized microbial cells. Observations were initially made on yeast floccule characteristics during fermentation. An aeration-type fluidized-bed bioreactor that retained virtually all the yeast particles was built and operated continuously for 3 months. Bioreactor operation was found to be quite favorable for this fermentation system. The yeast concentration exceeded 40 g (dry mass)/liter; delivery of a limited amount of supplementary oxygen enhanced throughput to give levels as high as 20-24 g/liter.hr. The kinetic equations were also determined.

Ethanol↗

PubMed1989

[Serology of typhoid fever in children. I. Capillary flocculation- agglutination. Its specificity in an asymptomatic population and its utility at a pediatric emergency service].

Using a capillary flocculation technique we evaluated serum samples of asymptomatic children for typhoid fever serology. Thirty one (5.16%) of the 600 serum samples tested were positive for a specificity of 95%. To evaluate the sensitivity of the test, serum samples from 36 children with proven typhoid fever and a similar number of control patients were evaluated. The sensitivity of the capillary flocculation test in this group was 100%. The test compared favorably with the Ruiz Castañeda serologic test for typhoid fever.

Adolescent↗

PubMed1978

[Use of an immunofluorescence method and a flocculation test with DNA-sensitized bentonite particles in the serodiagnosis of disseminated lupus erythematosus (SLE)].

The determination of antibodies against native DNA is of great importance in the solution of the diagnostic and therapeutic problems of dissiminated lupus erythematodes. The practical results are in a direct dependence on the laboratory methods for their determination. The diagnostic significance of two methods was studied with the present investigation: indirect immunofluorescent test and flocculation test with DNA-sensibilized bentonite particles. Under the conditions of the investigation, with the aid of the first method, antibodies against native DNA were found in 86.1 per cent of the sera of lupus nephropathy patients as well as in 13.3 per cent of the sera of patients with renal diseases not associated with LED. High serum titres including up to 1/128, were observed only in LED cases. The continuous persistence of antibodies against LED is also characteristic for the latter. The flocculation test was positive in 60.7 per cent of the sera investigated only with LED cases. The conclusion is that both methods could more wisely be used in LED immunodiagnostic because they combine high sensitivity with specificity of reaction, are easy to perform and no expensive material and apparatuses are required.

Adolescent↗

PubMed1982

[Elimination of bacteria and viruses by flocculation in treated sewage].

In laboratory experiments the elimination of bacteria and viruses in treated sewage by different flocculants varied between 47.9 and 99.5%. Ferric and aluminum chloride reduced both groups of microorganisms in a greater extent than polyelectrolytes, among those the cationic polymers were better suitable than nonionic and anionic types. With a combination of an anorganic flocculant and an polyelectrolyte no increased effect was seen according to the elimination of the colony number and the number of viruses.

Aluminum↗

PubMed1993

[Inactivation of bacteria and coliphages in surface water highly polluted by secondary effluent and purified by flocculation and filtration by means of UV irradiation at a pilot plant scale].

The water of a channel in Berlin which is highly polluted by municipal sewage effluent is treated at the phosphate elimination plant (PEP) Tegel by flocculation and filtration in order to reduce eutrophication in the following Lake Tegel. The elimination of bacteria and coliphages in the effluent of the PEP was investigated in a scale pilot UV irradiation reactor installed at the outlet of the PEP Tegel. The influence of technical parameters such as flow rate and the arrangement of 23 UV lamps in the reactor on the inactivation was tested. The UV irradiation dose was calculated 119 mJ/cm2 and 49 mJ/cm2 at a flow rate of 50 m3/h and 120 m3/h, respectively and for an irradiation zone of 97.5 cm. The colony count of bacteria and concentrations of coliform organisms, E. coli, and feacal streptococci as well as the plaque forming units of coliphages in the influent of the UV reactor were reduced 2-3 lg units by an irradiation dose of 119 mJ/cm2. These elimination was found being only one lg unit at a UV irradiation dose of 49 mJ/cm2. The concentration of E. faecalis and Coliphages f2 seeded into the influent of the UV reactor decreased after UV irradiation by 119 mJ/cm2 by 2-4 lg units and 1-2 power of magnitude, respectively. A UV dose of 49 mJ/cm2 caused only a 90% elimination of E. faecalis and a 75% inactivation of Coliphages f2. Due to heterogenous distribution and the different retention period of the inflowing water in the irradiation zone, the inactivation of E. faecalis and Coliphages f2 was unequal. Both test organisms decreased in the middle of the reactor up to 2 lg units more than at the sides of the reactor. The hygienic-microbiological quality of a secondary effluent from sewage treatment plants can be improved by a combination of flocculation-filtration and UV irradiation due to their additive elimination effect. However, this UV reactor, which was tested under field conditions can only ensure the inactivation of bacteria and coliphages in the pretreated effluent, if more homogenous distribution of the inflowing water can be achieved. Further, the water must be irradiated by a higher UV dose.

Coliphages↗

PubMed1996

Flocculation of Esch. coli with cationic polymers: a model for the dose curve based on charge.

Continuously grown cells from a glucose limited chemostat were flocculated with four different cationic polymers. The polymer was added to the cells either dropwise or as a slug at the start of the flocculation period. Dose curves for each polymer type and using each method of polymer addition were constructed. It was evident that classical overdose was possible with all four polymers if slug addition was used. Continuous addition produced dose curves overdose was possible with all four polymers if slug addition was used. Continuous addition produced dose curves with no overdosing except when low molecular weight, low charge density polymer was used. The dose curves could be combined if they were based on amount of charge added. The dose curve was not linear, but fitted a logarithmic model well. Charge density was much more important than MW of the polymer.

Biotechnology↗

PubMed1977

Effect of mass transfer resistance on the Lineweaver-Burk plots for flocculating microorganisms.

It is shown that the mass transfer resistance can significantly distort the linearity of the Lineweaver-Burk plot of the kinetic data for a microbial culture which forms aggregates. For small flocs, the linearity of the Lineweaver-Burk plot is largely retained, but a different slope and intercept will be obtained compared with flocs free from mass transfer resistance. For large flocs, the Lineweaver-Burk plot shows pronounced curvature at high limiting substrate concentrations. Hence, if the true intrinsic kinetic parameters are to be extracted from a highly flocculating microbial culture, sufficient agitation has to be provided to remove the effect of mass transfer resistance. If the behavior of the flocculating microbial culture is to be explored, additional values for some physical parameters, such as the effective diffusion coefficient of the substrate in floc, the floc density, and the mean floc radius, are needed.

Bacterial Physiological Phenomena↗

PubMed1996

Mechanism of Particle Flocculation by Magnetic Seeding

Magnetic seeding flocculation of micrometer-sized particles in liquid suspensions is investigated. Primary forces acting on individual particles, including gravity and magnetic attraction, as well as van der Waals, electrostatic, magnetic dipole, and hydrodynamic interparticle forces, are examined and quantified. A mathematical statement of the overall relative velocity is developed from the net force acting on a particle. From this, the equation of relative motion for two particles in cylindrical coordinates is derived. A computer model is then used to solve this equation repeatedly to find the particle trajectory borderline between collision and noncollision, thus determining the collision efficiency and collision frequency. The effects of a variety of parameters on flocculation performance are then explored. It is found that some factors have unexpected and complex influences on the collision efficiency and collision frequency, particularly the particle size ratio and the direction of the magnetic field.

Journal Article↗

PubMed1997

Modeling of Combined Creaming and Flocculation in Emulsions

A computer model is presented which simulates the simultaneous creaming and flocculation of emulsions. A cubic lattice model is used, with particles bonding together and breaking apart according to predefined probabilities. Creaming and diffusion are included, with different rates for different sizes of floc. Results are presented in the form of concentration profiles as a function of height, and as the variation of the pseudo-fractal dimension of the particle networks formed. In the numerical simulations, an increase in creaming rate was observed before a particle network formed which prevented further creaming. A sharp serum interface was seen. In the presence of bond breakage, creaming proceeded for a longer period and a more compact network was formed. These results explain some features observed experimentally in creaming and flocculating emulsions, but do not reproduce the rapid serum development seen in some cases.

Journal Article↗

PubMed1998

Rheology and Flocculation of Oil-in-Water Emulsions Made with Mixtures of alphas1-Casein + beta-Casein.

The influence of the composition of a mixed binary protein emulsifier composed of alphas1-casein + beta-casein on the rheology of concentrated oil-in-water emulsions (45 vol% oil, 5 wt% protein, pH 7) has been investigated over the temperature range 0-40 degreesC. Controlled stress viscometric data are reported over the shear stress range 0.1-30 Pa for systems with alphas1-casein/beta-casein ratios of 100:0, 98:2, 95:5, 90:10, 75:25, 50:50, and 0:100. The pure casein emulsions showed substantially different temperature-dependent rheology, and there was observed to be a pronounced maximum in the small-deformation complex modulus of the pure alphas1-casein emulsion in the range 30-40 degreesC. In the emulsions containing >/=90% alphas1-casein in the emulsifier mixture, all of the beta-casein present was found to be associated with the surface of the droplets. Average droplet sizes and protein surface coverages were higher in the mixed casein systems than in the equivalent pure casein systems. The strongly pseudoplastic character of the emulsions is consistent with extensive reversible flocculation caused probably by a depletion mechanism involving unadsorbed protein. The degree of flocculation is sensitive to temperature and to the alphas1-casein/beta-casein ratio. The results can be interpreted in terms of changes in protein self-assembly and adsorbed layer structure which influence the strength of the interdroplet interactions and hence the rheological behavior of the emulsions. There is some evidence of a specific role for alphas1-casein-beta-casein complexes in these systems. Copyright 1998 Academic Press.

Journal Article↗