Laboratory flocculation

Laboratory devices, gas-liquid mass transfer, 15 690-692 Laboratory extractors, 10 768 Laboratory flocculant testing, 11 638-639... 

Laboratory Flocculant Testing. The objective of laboratory testing of flocculants is lo determine which chemical composition and molecular weight will give the best cost performance. The usual method is lo simulate on a laboratory scale the formation of floes and then subject them to the same or similar types of forces as would be encountered in a full-scale dewatering device. 

Couette flocculators are basic research apparatuses of flocculation kinetics, and can be used with particle counters (e.g. Coulter counter) as a standard for other laboratory flocculators which have ill-defined velocity gradients. 

Attach the first set of sample beakers to the stirring device (a laboratory flocculator). 

Eor evaluation of flocculants for pressure belt filters, both laboratory-scale filters and filter simulators are available (52,53) in many cases from the manufacturers of the full-scale equipment. The former can be mn either batchwise or continuously the simulators require less substrate and are mn batchwise. The observed parameters include cake moisture, free drainage, release of the cake from the filter cloth, filter blinding, and retention of the flocculated material during appHcation of pressure. 

In the area of municipal and iadustrial wastewater treatment, the principal environmental issue is the toxicity of residual flocculating agents ia the effluent. Laboratory studies have shown that cationic polymers are toxic to fish because of the iateraction of these polymers with giU. membranes. Nonionic and anionic polymers show no toxicity (82,83). Other studies have shown that ia natural systems the suspended inorganic matter and humic substances substantially reduce the toxicity of added cationic polymer, and the polymers have been used successfully ia fish hatcheries (84—86). Based on these results, the EPA has added a protocol for testing these polymers for toxicity toward fish ia the presence of humic acids (87). The addition of anionic polymers to effluent streams containing cationic polymers to reduce their toxicity has been mentioned ia the patent Hterature (83). 

When the overflow clarity is independent of overflow rate and depends only on detention time, as in the case for high soHds removal from a flocculating suspension, the required time is deterrnined by simple laboratory testing of residual soHd concentrations in the supernatant versus detention time under the conditions of mild shear. This deterrnination is sometimes called the second-order test procedure because the flocculation process foUows a second-order reaction rate. 

Precipitation and flocculation can be integrated into more complex treatment systems. The performance and reliability of these processes depends greatly on the variability of the composition of the waste being treated. Chemical addition must be determined using laboratory tests and must be adjusted with compositional changes of the waste being treated or poor performance will result. 

In a series of experiments on the flow of flocculated kaolin suspensions in laboratory and industrial scale pipelines(26-27-2Sl, measurements of pressure drop were made as a function of flowrate. Results were obtained using a laboratory capillary-tube viscometer, and pipelines of 42 mm and 205 mm diameter arranged in a recirculating loop. The rheology of all of the suspensions was described by the power-law model with a power law index less than unity, that is they were all shear-thinning. The behaviour in the laminar region can be described by the equation ... 

Honeyman and Santschi 1989). Therefore, flocculation of colloids to form settling particles in estuaries is an important mechanism for trace element removal (Sholkovitz 1977). This is particularly true of Fe, which is a ubiquitous colloidal species and is removed at low salinities. Additional removal may occur by adsorption onto floes, as demonstrated by mixing of organic-rich waters with seawater in the laboratory (Sholkovitz 1977). 

In part II of the present report the nature and molecular characteristics of asphaltene and wax deposits from petroleum crudes are discussed. The field experiences with asphaltene and wax deposition and their related problems are discussed in part III. In order to predict the phenomena of asphaltene deposition one has to consider the use of the molecular thermodynamics of fluid phase equilibria and the theory of colloidal suspensions. In part IV of this report predictive approaches of the behavior of reservoir fluids and asphaltene depositions are reviewed from a fundamental point of view. This includes correlation and prediction of the effects of temperature, pressure, composition and flow characteristics of the miscible gas and crude on (i) Onset of asphaltene deposition (ii) Mechanism of asphaltene flocculation. The in situ precipitation and flocculation of asphaltene is expected to be quite different from the controlled laboratory experiments. This is primarily due to the multiphase flow through the reservoir porous media, streaming potential effects in pipes and conduits, and the interactions of the precipitates and the other in situ material presnet. In part V of the present report the conclusions are stated and the requirements for the development of successful predictive models for the asphaltene deposition and flocculation are discussed. 

One major question of interest is how much asphaltene will flocculate out under certain conditions. Since the system under study consist generally of a mixture of oil, aromatics, resins, and asphaltenes it may be possible to consider each of the constituents of this system as a continuous or discrete mixture (depending on the number of its components) interacting with each other as pseudo-pure-components. The theory of continuous mixtures (24), and the statistical mechanical theory of monomer/polymer solutions, and the theory of colloidal aggregations and solutions are utilized in our laboratories to analyze and predict the phase behavior and other properties of this system. 

Sengco, M., Removal of red and brown tide cells using clay flocculation I. Laboratory culture experiments with Gymnodinium breve and Aureococcus anophagejferens. Mar. Ecol. Prog. Ser., 2003. 

Addition of fuel oil no. 2 to a laboratory marine ecosystem showed that the insoluble, saturated hydrocarbons in the oil were slowly transported to the sediment on suspended particulate material. The particulate material contained 40-50% of the total amount of aliphatics added to the system and only 3-21% of the aromatic fraction (Oviatt et al. 1982). This indicates that most aromatic hydrocarbons are dissolved in the water (Coleman et al. 1984), whereas the aliphatic hydrocarbons are not (Gearing et al. 1980 Oviatt et al. 1982). In a similar experiment, when fuel oil no. 2 was added continuously to a marine ecosystem for 24 weeks, oil concentrations in the sediment remained low until 135 days after the additions began, but then increased dramatically to levels that were 9% of the total fuel oil added (108 g/tank) and 12% of the total fuel oil saturated hydrocarbons. The fuel oil concentrations in the sediment began to decrease quite rapidly after the maximum levels were reached. The highest sediment concentrations of saturated hydrocarbons (106-527 g/g) were found in the surface flocculent layer, with concentrations decreasing with sediment depth from 22 g/g to not detectable at 2-3 cm below the sediment surface. 

The generation of colloidal charges in water.The theory of the diffuse electrical double-layer. The zeta potential. The flocculation of charged colloids. The interaction between two charged surfaces in water. Laboratory project on the use of microelectrophoresis to measure the zeta potential of a colloid. 

Numerous studies have been conducted on the nature of the dissolved and particulate organic matter in natural waters. In general, these studies have shown that the composition of the bulk of the organic matter is undefined. Many of the laboratory studies on the nature of the dissolved organic matter in natural waters are of limited value owing to possible alteration of the compounds by the concentration and analytical methods used. The selectivity of the methods used to concentrate the solute to analytically detectable levels presents another problem in many analytical procedures used to study trace compounds in natural waters. Concentration procedures such as freezing, flocculation, sorption columns, and solvent extraction, have been shown to be selective for certain types of compounds (32, 34, 38). Extreme care must be exercised to insure... 

Tphe kinetics of the protease-triggered clotting of blood and milk has been formulated in a number of recent publications from this laboratory (1,2,3). In milk clotting, the coagulation is initiated through the limited proteolysis of -casein, the milk protein component which normally protects the casein micelles from flocculation by calcium ions (4). Kappa-casein is a single polypeptide chain of 169 residues, the sequence... 

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