Biological wastewater treatment, particle

Particle removal during biological wastewater treatment... 

Biological treatment would seldom be selected as the primary means of treating a CMP wastewater, but it is useful to consider the fate and potential impacts of alumina, ceria, and silica particles in a biological wastewater treatment process. At many fabs, waste-water is pretreated and discharged to a municipal wastewater treatment system where dilute industrial waste effluents are combined with municipal sewage flows and treated in a biological wastewater treatment process. Some fabs have an onsite biological wastewater treatment process, but they are believed to be in the minority. 

Alumina, ceria, and silica particles are removed in biological wastewater treatment processes by a combination of aggregation, heteroaggregation, and sorption onto biosolids and/or extracellular polymeric substances. Some studies indicate that silica particles are less easily removed than ceria and aluminum particles. Most information on alumina, ceria, and silica removal in biological wastewater systems is from pilot- or laboratory-scale experiments, and relatively few smdies involving real CMP... 

A review of the wastewater treatment literature suggests a number of research needs. Efforts to characterize alumina, ceria, and silica particles in both waste materials and natural water systems face difficult metrology challenges. There is a need for vahdated methodologies that can discriminate quantitatively between individual types of nanomaterials and evaluate concentration by size, number count, and mass concentration within real environmental matrices. The few published evaluations of alumina, ceria, and silica nanoparticle removal in wastewater treatment processes have primarily addressed removal in municipal-type biological wastewater treatment processes whereas relatively little information is available regarding alumina, ceria, and silica nanoparticle removal in the types of physicochemical treatment processes that are often used by fabs to pretreat wastewaters prior to discharge. 

The experimental aspects of this study were focussed on two hard-water lakes in Switzerland, namely, the northern basin of Lake Zurich and Lake Sempach. The hydraulic residence time of Lake Zurich is 1.2 years. Most of the particles in the lake are produced directly or indirectly by biological processes within the lake itself (e.g., photosynthesis, CaC03 precipitation). Phosphorus removal has been implemented in recent years at all wastewater treatment plants discharging into the lake at present Lake Zurich can be described as between meso- and eutrophic. Lake Sempach has an average hydraulic residence time of 15.8 years as in Lake Zurich, particles in the lake waters are primarily autochthonous. Phosphorus concentrations have increased substantially and the lake is eutrophic. 

Stability in mixtures of colloidal particles and polymer molecules, dispersed in a solvent, has been the subject of experimental and theoretical investigations for a long time and it has applications in diverse fields such as paint technology, wastewater treatment, emulsion polymerization, biology etc. It has now been well recognized that polymer molecules can be used to induce either stabilization or flocculation (phase separation) in colloidal dispersions. It is important to distinguish between polymers which are adsorbed on the particle surface and those that are free in solution because the two situations usually lead to qualitatively different effects. Stability imparted by adsorbed polymers is known as steric stabilization and the flocculation or phase separation caused by the free polymer is due... 

Three-phase fluidized beds can be used as bioreactors for aerobic biochemical processes, including both fermentation processes and wastewater treatment. The gas phase is air, required for biological growth, while the solid particles provide immobilized surfaces on or in which cell growth can occur. The aqueous liquid phase provides the culture medium needed for the growth and maintenance of the cells. Air may be introduced separately from the liquid, or be premixed with the aqueous medium. The liquid medium may exhibit non-Newtonian rheology. A disadvantage of three-phase... 

Treatment processes for wastewater reuse and water treatment usually have adopted process such as biological treatment, coagulation, sand filtration, membrane filtration and activated carbon adsorption [168]. Recently, membrane filtration in water treatment has been used worldwide for reduction of particle concentration and natural organic material in water. Among the membrane processes, nanofiltration (NF) is the most recent technology, having many applications, especially for drinking water and wastewater treatment [169]. 

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