Coagulation sedimentation process

Minegishi, S., Jang, N.-Y., Watanabe, Y., Hirata, S., and Ozawa, G. (2001). Fouling mechanism of hollow fibre ultrafiltration membrane with pre-treatment by coagulation/sedimentation process. 

X 10 kkg/year, respectively]. Wastewater consists of direct contact process water, noncontact blowdown, and noncontact ancillary water. The total flow of contact water is approximately 1.27 x 10 mVday (3.355 x 10 gpd), and the total flow of noncontact water is 340.4 mVday (9 X 10" gpd). Treatment of the wastewater consists of coagulation, sedimentation, and biological treatment with extended aeration. Treated wastewater is discharged to a surface stream. 

The initial distribution of radioaerosols from an atmospheric nuclear explosion depends upon condensation and coagulation during the rise and cooling of the fireball. These processes result in small particle sizes of the nuclear weapon debris. For example, Stewart (24) calculated that for yields of about 20 kilotons, the particles coagulated from vaporized materials will reappear as very small particles (with modal radii of the order of 0.1 to 0.01 fi) and remain airborne for long periods. When such particles are carried into the stratosphere by the buoyant lifting of the fireball, it is expected that they will become a quasi-conservative constituent of the stratospheric air. It has been shown that particles with diameters less than lfi have an essentially infinite residence in the atmosphere for sedimentation processes alone (16). 

The current version of GEM-AQ has five size-resolved aerosols types, viz. sea salt, sulphate, black carbon, organic carbon, and dust. The microphysical processes which describe formation and transformation of aerosols are calculated by a sectional aerosol module (Gong et al. 2003). The particle mass is distributed into 12 logarithmically spaced bins from 0.005 to 10.24 pm radius. This size distribution leads to an additional 60 advected tracers. The following aerosol processes are accounted for in the aerosol module nucleation, condensation, coagulation, sedimentation and dry deposition, in-cloud oxidation of SO2, in-cloud scavenging, and below-cloud scavenging by rain and snow. 

Colloids can be organic or inorganic. Even if they are not separated from the dissolved load by classical filtration, colloids have the physicochemical properties of a solid. Colloids are finely divided amorphous substances or sohds with very high specific surface areas and strong adsorption capacities. It is shown by Ferret et al. (1994) for the Rhine River that the colloids contribute less than 2% of the total particle volume and mass, but represent a dominant proportion of the available surface area for adsorption of pollutants. The abundance of colloids, their fate, through coagulation and sedimentation processes in natural waters therefore control the abundance of a number of elements. 

The coagulation process was investigated by the jar-test method with the following parameters rapid mix (G = 200 s ) for 2 minutes, flociUation (G = 20 s ) for 20 minutes, and sedimentation for 30 minutes. After the sedimentation process had been completed, determinations were carried... 

The use of flotation for liquid-solid separation may compensate for some of these limitations of the sedimentation process for suspensions with less optimal floe formation. This effect was observed in particular if suspensions were coagulated with Al3+. 

Kiprboe, T., Lundsgaard, C., Olesen, M., Hansen, J. L. S., 1994. Aggregation and sedimentation processes during a spring phytoplankton bloom a field experiment to test coagulation theory. Journal of Marine Research, 52, 297-323. 

The interaction in a two-body collision in a dilute suspension has been expanded to provide a useful and quantitative understanding of the aggregation and sedimentation of particulate matter in a lake. In this view, Brownian diffusion, fluid shear, and differential sedimentation provide contact opportunities that can change sedimentation processes in a lake, particularly when solution conditions are such that the particles attach readily as they do in Lake Zurich [high cc(i,j)exp]. Coagulation provides a conceptual framework that connects model predictions with field observations of particle concentrations and size distributions in lake waters and sediment traps, laboratory determinations of attachment probabilities, and measurements of the composition and fluxes of sedimenting materials (Weilenmann et al., 1989). 

Removal or loss of a particle of a given size from a volume of fluid is assumed to occur through only two physical processes sedimentation and coagulation. Sedimentation removes particles from the volume of fluid, while coagulation transfers many smaller particles into fewer larger particles within the fluid volume. 

Usually, in a conventional coagulation-filtration process for arsenic removal, the addition of the coagulant is followed by a short rapid-mix step followed by a slow-mix step for flocculation. Flocculation is usually followed by sedimentation and filtration. To do away with the multitude of steps required in the conventional process, the authors designed and tested a simplified iron coagulation-direct mi-croflltration process, as described below (3,4). 

Flocculation leads to strongly reduced interparticle distances. Also, the sedimentation process alters the particle distribution throughout the system, leading to a particle density gradient. The size distribution will change as a result of coalescence or coagulation. 

Because of the rapid modifications of the physicochemical and microbiological characteristics of natural water samples, initiated by changes in temperature, pH, depth, dissolved O2 or CO2, light, and convection, aquatic samples should be processed for electron microscopy without any delay to avoid dissolutions, precipitations, coagulations, sedimentations, microbial growth, or shifts in chemical... 

Chemical coagulation has been in practice for several decades to precipitate the soluble heavy metals present in the waste water, as hydroxides and facilitate their removal by physical separation through sedimentation process. Ferrous sulphate, hydrated lime, alum, etc. are the most common chemical coagulants being used in Industries. 

As an oxidant, ozone removes iron, odors, and sometimes color, from water. It is used to oxidize organic substances in water, so they can he more easily removed in subsequent processes, i.e., coagulation, sedimentation, and filtration. Occasionally, ozone is combined with peroxide to increase its oxidation potential (peroxone). Peroxone can remove a wide variety of organic contaminants. 

The production, transport and processing of polymer dispersions expose these materials to significant degree of mechanical and thermal stress, which can lead to coagulation, sedimentation, phase separation or changes in viscosity. These changes are generally due to instabilities of the polymer particles. 

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