[Study of the flocculation reaction in the diagnosis of amebiasis].
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Amebiasis↗
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Modelling of floc-bubble aggregate rise rates in dissolved air flotation.
The use of relatively simple, but conceptually sound mathematical models, is a powerful tool to identify and understand parameters that are critical to a process. In this paper, a model is presented which addresses the rise rate of floc-bubble aggregates in the DAF separation zone. The model uses Stoke's Law as a point of departure, which is then progressively extended to incorporate the non-sphericity of the aggregates, the non-laminar nature of their movement, the fractal nature of the flocs, the physical constraints of attaching bubbles to a floc, and the limit on bubble numbers imposed by a typical air dosing system. The main findings are: There are two distinctly different DAF domains, namely a small floc domain and a large floc domain. In the small floc domain, the bubble size, the air volume, chemical dosing and the degree of flocculation have to be optimized and accurately controlled, while the large floc domain is less sensitive to these parameters. The calculated rise rates are significantly lower than some of the latest pilot testing results reported from the USA; a surprising finding at first. There are, however, numerous modelling simplifications that may explain this discrepancy. The most probable reasons are the further agglomeration of the aggregates in the separation zone due to differential rise rates or the recirculating flow within the white-water blanket, and the complex and poorly understood flow patterns within the separation zone.
Air↗
Treatment of pulp and paper mill wastewater by polyacrylamide (PAM) in polymer induced flocculation.
The flocculation performances of nine cationic and anionic polyacrylamides with different molecular weights and different charge densities in the treatment of pulp and paper mill wastewater have been studied. The experiments were carried out in jar tests with the polyacrylamide dosages range of 0.5-15 mg l(-1), rapid mixing at 200 rpm for 2 min, followed by slow mixing at 40 rpm for 15 min and settling time of 30 min. The effectiveness of the polyacrylamides was measured based on the reduction of turbidity, the removal of total suspended solids (TSS) and the reduction of chemical oxygen demand (COD). Cationic polyacrlyamide Organopol 5415 with very high molecular weight and low charge density is found to give the highest flocculation efficiency in the treatment of the paper mill wastewater. It can achieve 95% of turbidity reduction, 98% of TSS removal, 93% of COD reduction and sludge volume index (SVI) of 14 ml g(-1) at the optimum dosage of 5 mg l(-1). SVI values of less than 70 m lg(-1) are found for all polyacrylamide at their respective optimum dosage. Based on the cost evaluation, the use of the polyacrylamides is economically feasible to treat the pulp and paper mill wastewaters. This result suggests that single-polymer system can be used alone in the coagulation-flocculation process due to the efficiency of the polyacrylamide. Sedimentation of the sludge by gravity thickening with settling time of 30 min is possible based on the settling characteristics of the sludge produced by Organopol 5415 that can achieve 91% water recovery and 99% TSS removal after 30 min settling.
Acrylic Resins↗
Adsorption of cationic polyelectrolyte at the solid/liquid interface and dispersion of nanosized silica in water.
Adsorption of cationic polyelectrolyte, a homopolymer of maleimide propyl trimethylammonium chloride (MPTMAC), on silica nanoparticles from aqueous solution was studied. The adsorbed amount of MPTMAC and the adsorption layer thickness from solutions of different pH, polyelectrolyte concentration, salt type, and salt concentration were measured. The adsorbed amount exhibited a maximum as a function of the electrolyte concentration. The onset of the decline in the adsorbed amount depended on the type of counterions. The thickness of the adsorption layer increased gradually with increased of electrolyte concentration and leveled off at high electrolyte concentration. The enhanced adsorption in the presence of Na2SO4 can be explained by the bivalent SO4(2-) causing a better shielding effect. With increasing pH the adsorbed amount of MPTMAC increased, whereas the thickness of an adsorbed layer of MPTMAC decreased. At low polyelectrolyte concentrations unstable silica suspensions were observed from a stability test. At high polyelectrolyte concentrations the higher particle coverage caused electrosteric stabilization of the dispersion. However, further increase in MPTMAC concentration after saturated adsorption would flocculate the dispersed system. At low pH, MPTMAC tending to create a loops or tails conformation stabilized the suspension.
Journal Article↗
Pre-coagulation for microfiltration of an upland surface water.
The effect of different coagulants on cake formation and hydraulic resistance in membrane filtration of strongly coloured (SUVA> or =4.8) upland surface water has been studied at bench-scale under constant pressure conditions. Coagulants used were aluminium sulphate, polyaluminium chloride, ferric chloride and ferric sulphate. Optimisation of coagulation parameters was carried by conventional jar testing. The R'c (specific cake resistance in m(-2)) values were determined for all coagulants over a range of coagulant doses and slow mixing flocculation periods. Experiments indicated slight differences in cake formation trends between ferric- and aluminium-based coagulants and chloride and sulphate counterions, but that the range of measured R'c values was small (0.9 and 2.6 x 10(18) m(-2)) over the range of doses studied. Greater than 99% UV(254) removal was achieved with every coagulant, whereas dissolved organic carbon (DOC) removal ranged from 78% to 88%. Optimisation of the pre-coagulation-membrane filtration process suggests ferric chloride to be slightly superior for the feedwater matrix studied on the basis of DOC removal, whereas ferric sulphate gave slightly lower filter cake specific resistance values.
Filtration↗
[Comparison of different methods for the detection of enteroviruses in drinking water].
UNLABELLED: Detection of enteroviruses in drinking water poses a very specific problem, since a very small number of particles have to be identified in huge water quantities. Currently, there are a number of methods to identify the concentration of virus particles and RNA templates to carry out RT-PCR, however, no standard method has yet been proposed. AIM: The aim of this report is to suggest optimal methods for the preparation of RNA templates to carry out RT-PCR. MATERIAL AND METHODS: In this experimental study, two different methods were employed on preparing RNA template. The concentration of virus particles in a large (10 L) and small (1 L) quantity of water was determined by use of the electropositive microporous virology filter (method 1 and method 2). Elution and flocculation of the virals particles were performed by organic extraction (method 1) and inorganic extraction (method 2). The sensitivity of the methods was assessed by testing the artificially contaminated water with 10(1) to 10(5) virus-particles using 1-L and 10-L containers of water. RESULTS: Method 1 detected 10(5) and 10(4) virus particles, method 2 10(5), 10(4) and 10(3) virus particles from 10 L and 1 L of water, respectively, yielding a statistically significant difference (p<0.01; chi2 = 6.061). Using two-step RT-PCR with nested PCR method, enteroviruses were detected in 42/100 (42%) samples of surface drinking water and in 83% of the same samples using RT-PCR without nested PCR.
Enterovirus↗
[The T-66 flocculation reaction in epidemic hepatitis and other diseases associated with jaundice].
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Hepatitis A↗
[Evaluation of the sanitary-and-epidemiological safety of flocculating agents used for portable water purification].
Polyelectrolytes used in the practice of water supply to the population were comparatively hygienically studied, by using a complex of hazard indices and a new approach to sanitary-and-epidemiological evaluation of the safety of water-soluble polymers is substantiated. The anionic and cationic flocculating agents from different chemical classes, such as Superflok A-100, Fennopol A 321E, Fennopol K 221E, Praestol 2530 TR, VPK-402, Superflok C-577, Saipan, KF-91, Ecosol-401, a low molecular-weight sodium polyacrylate were tested as model compounds. Moreover, the information already available in the scientific literature on the toxicity of synthetic polyelectrolytes was analyzed. The generalized maximum permissible concentrations were substantiated for individual chemical classes of synthetic polyelectrolytes: polyacrylamides, polyamines, polydiallyldimethylammonium chloride.
Acrylic Resins↗
Mutagenic activity in humic water and alum flocculated humic water treated with alternative disinfectants.
Mutagenic activity in Salmonella typhimurium strains TA 100, TA 98 and TA 97 has been determined for humic water and alum flocculated humic water, treated with the alternative disinfectants chlorine, ozone, chlorine dioxide, ozone/chlorine and chlorine/chlorine dioxide. The most pronounced activity was found for chlorine treated water tested on strain TA 100 without metabolic activation (S9 mix). Ozone treatment prior to chlorination did not alter the activity, while treatment with chlorine in combination with chlorine dioxide reduced the activity to a level somewhat over the background. No mutagenic response was detected in waters treated with ozone or chlorine dioxide alone. In presence of S9 mix all water extracts studied were non-mutagenic.
Alum Compounds↗
A biometric study of higher alcohol production in Saccharomyces cerevisiae.
A hundred strains of Saccharomyces cerevisiae were examined for the ability to produce higher alcohols. In the strains tested the production of higher alcohols was found to be an individual strain characteristic and, as such, was statistically significant. The characteristics of the strains used (flocculation ability, foaming ability, killer character, and non-H2S production) were found to be uncorrelated to isobutanol and isoamyl alcohol production, whereas the production of high levels of n-propanol was found to be related to inability to produce H2S. This, in turn, suggests a link to methionine biosynthesis.
Alcohols↗
Beneficial effects of humic acid on micronutrient availability to wheat.
Humic acid (HA) is a relatively stable product of organic matter decomposition and thus accumulates in environmental systems. Humic acid might benefit plant growth by chelating unavailable nutrients and buffering pH. We examined the effect of HA on growth and micronutrient uptake in wheat (Triticum aestivum L.) grown hydroponically. Four root-zone treatments were compared: (i) 25 micromoles synthetic chelate N-(4-hydroxyethyl)ethylenediaminetriacetic acid (C10H18N2O7) (HEDTA at 0.25 mM C); (ii) 25 micromoles synthetic chelate with 4-morpholineethanesulfonic acid (C6H13N4S) (MES at 5 mM C) pH buffer; (iii) HA at 1 mM C without synthetic chelate or buffer; and (iv) no synthetic chelate or buffer. Ample inorganic Fe (35 micromoles Fe3+) was supplied in all treatments. There was no statistically significant difference in total biomass or seed yield among treatments, but HA was effective at ameliorating the leaf interveinal chlorosis that occurred during early growth of the nonchelated treatment. Leaf-tissue Cu and Zn concentrations were lower in the HEDTA treatment relative to no chelate (NC), indicating HEDTA strongly complexed these nutrients, thus reducing their free ion activities and hence, bioavailability. Humic acid did not complex Zn as strongly and chemical equilibrium modeling supported these results. Titration tests indicated that HA was not an effective pH buffer at 1 mM C, and higher levels resulted in HA-Ca and HA-Mg flocculation in the nutrient solution.
Alkanesulfonic Acids↗
Production of drug loaded microparticles by the use of supercritical gases with the aerosol solvent extraction system (ASES) process.
The aerosol solvent extraction system (ASES) uses a supercritical gas as non-solvent for an organic solution of drug and polymer in order to form microparticles by a flocculation process. Due to the miscibility of organic solvent and supercritical gas phase, microparticles with residual organic solvents below 30 ppm are formed. This principle was tested to encapsulate model drugs such as hyoscine butylbromide, indomethacin, piroxicam and thymopentin. As a carrier, the polymer poly-L-lactide was used. The resulting microparticles were investigated with regard to particle formation, morphology, particle size, size distribution, and drug loading. With decreasing, polarity of the incorporated drug, an increasing extraction occurs which lowers the drug loading of the microparticles. The extraction capacity of the gas phase depends on temperature and pressure which determines density and polarity of the gas. The obtained results show that the production conditions have to be optimized for each drug/polymer combination. Totally non-polar drugs are completely extracted together with the organic solvent, however, polar drugs, and here especially peptides and proteins, are easy to incorporate with the ASES process.
Aerosols↗
Flocculation tssts in women taking oral contraceptives.
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Chemical and Drug Induced Liver Injury↗
[Flocculation of serum proteins as related to hydrogen-ion concentration].
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Blood Proteins↗
Storage of brewing yeasts by liquid nitrogen refrigeration.
Many yeast strains are difficult to maintain in culture in a stable state, and long-term preservation by lyophilization, which has proved useful for other fungi, has given poor results with brewing yeasts. As an alternative to continuous subculture, which maximizes strain variability, various methods of cryogenic storage were investigated. Yeast strains were frozen with or without cryoprotectants (such as glycerol or inositol) and stored at -196 C. Recovery after warming was estimated from plate counts, and survivors were screened to detect changes in the frequency of morphological types, respiratory-deficient mutants, and glycerol-sensitive mutants. Strains varied in their sensitivity to freezing, and survival was modified by the growth medium, the freezing munstrua, and the freezing conditions. Suspension of cells in 10% (vol/vol) glycerol, cooled at 1 C/min, warmed rapidly and plated on malt-yeast extract-glucose-peptone agar produced the highest percentage of viable colonies with a minimal change in metabolic characteristics. In two of the strains tested, no significant increase in mutation rate was detected under any of the treatments; the strains were maintained in a stable state and were metabolically comparable to unfrozen strains. In one strain of Saccharomyces uvarum after some freezing treatments, the percentage of respiratory-deficient mutants increased markedly, the fermentation rate declined, and a loss of flocculation occurred. The freezing parameters which increased the level of respiratory-deficient cells should be avoided in maintaining this strain. Maintenance of cultures of brewing yeasts by cryogenic storage has several advantages over other preservation techniques: the method is simple and reproducible, the cultures have remained stable over a 3-year test period, and the viability is high.
Journal Article↗
Preparation and release studies of alkannin-containing microcapsules.
Microcapsules containing the pharmaceutical substance alkannin were prepared by the solvent evaporation method to enhance alkannin stability (reduce photo-oxidation, polymerization), to decrease its hydrophobicity and to control its release rate. The effect of various parameters, such as the type of polymeric matrix, the type of surfactant used for microcapsules preparation and the addition of Pistacia lentiscus resin in the core, on the characteristics of the produced microcapsules and the release rate of alkannin were investigated experimentally. Among the polymers tested for matrix, ethylcellulose of viscosity 46cp was the most successful, while ethylcellulose 10cp gave microcapsules with good morphological characteristics but high release rate. Beeswax resulted in flocculation and P. lentiscus resin with or without colophony as the matrix resulted in compact particles with no pores and much slower release, but did not allow alkannin to release easily from the matrix. Sodium dodecyl sulfate resulted in microcapsules with desirable morphological and physicochemical characteristics, while acacia and tragacanth gums were not indicated as surfactants in alkannin microencapsulation since they gave a high release rate and a great extent of particle size, respectively. The incorporation of Pistacia lentiscus resin in the capsule core increased loading and microencapsulation efficiency. Ethylcellulose of 46cp viscosity with sodium dodecyl sulfate as surfactant had the best characteristics studied for alkannin microencapsulation. Finally, the dissolution rate of alkannin from microcapsules was studied in a simulated intestinal and gastric environment and an external environment. Alkannin-containing microcapsules with improved properties can be used internally and externally as a new drug-delivery system.
Capsules↗
Immunological studies on the localization of phosphatidylglycerol in the membranes of Mycoplasma hominis.
Phosphatidylglycerol is the main component (87%) of the membrane phospholipids of Mycoplasma hominis. It is immunologically active. Antibodies directed against phosphatidylglycerol were detected in rabbits intravenously immunised with native M. hominis or isolated M. hominis membranes. The intravenous method of immunisation was chosen in order to select for a response to surface antigenic determinants. Anti-phosphatidylglycerol antibodies were induced in rabbits by intravenously injecting the flocculated complexes of methylated bovine serum albumin and a phosphatidylglycerol/phosphatidylcholine/cholesterol mixture. These antibodies were specifically bound to intact M. hominis, as shown by complement fixation and Coombs tests. Native M. hominis were not agglutinated by anti-phosphatidylglycerol antibodies; but after partial digestion of the membrane proteins with Pronase, the mycoplasmas were heavily agglutinated by the anti-phosphatidylglycerol antibodies. The same amount of anti-phosphatidylglycerol antibodies was bound to intact M. hominis, containing 600 mug of phosphatidylglycerol as to 6 mug of phosphatidylglycerol in the optimal configurational arrangement of a mixed phosphatidylglycerol/phosphatidylcholine/cholesterol micelle. It is concluded that the major part of the phosphatidylglycerol in native M. hominis membranes is masked, probably by membrane proteins, and is not accessible to the anti-phosphatidylglycerol antibodies.
Agglutination Tests↗
Bilayer-forming synthetic lipids: drugs or carriers?
Since their introduction as bilayer-forming synthetic compounds in the eighties, dioctadecyldimethylammonium (DODA) and dihexadecylphosphate (DHP) salts have found many uses in strategic, applied areas. In particular, DODA chloride or bromide vesicles interacted with negatively charged prokaryotic or eukaryotic cells, yielding adsorption isotherms of high affinity for the cell surface, causing cell adhesion and flocculation, changing the cell surface charge from negative to positive, and causing loss of cell viability over DODA concentration ranges that depended on the cell type being tested. This work reviews data on DODA effects on cell viability (bacteria, fungus and cultured mammalian cells) to propose DODA salts as effective anti-microbial agents that exhibit differential cytotoxicity in vitro and, therefore, deserve to be investigated as potential drugs. The full utility of these inexpensive synthetic bilayers and bilayer fragments able to act as drugs themselves and, simultaneously, as drug, gene or vaccine carriers remains hitherto unexplored.
Animals↗