Suspended solid, definition

Depth tends to be determined from the retention time and the surface overflow rate. As surface overflow rates were reduced, the depth of sedimentation tanks was reduced to keep retention time from being excessive. It was recognized that depth was a valid design parameter and was more critical in some systems than retention time. As mixed-liquor suspended-solids (MESS) concentrations increase, the depth should also be increased. Minimum sedimentation-tank depths for variable operations should be 3.0 m (10 ft) with depths to 4.5 m (15 ft) if 3000 mg/L MESS concentrations are to be maintained under variable hydraulic conditions. With MESS concentrations above 4000 mg/L, the depth of the sedimentation tank should be increased to 6.0 m (20 ft). The key is to keep a definite freeboard over the settled-sludge blanket so that variable hydraulic flows do not lift the solids over the effluent weir. 

Starting point for evaluating the settling characteristics of suspended solids for dilute systems. Note that from the definition of the Reynolds number, we can readily determine the settling velocity of the particles from the application of the above expressions (u, = /xRe/dpp). The following is an interpolation formula that can be applied over all three settling regimes ... 

Traditionally, the definition of suspended solids as used in the characterization of wastewater is defined according to the method used in the analysis of total suspended solids (TSS), e.g., as described in Standard Methods for the Examination of Water and Wastewater (1998). This definition of suspended solids is based on a filtration—or sometimes also centrifugation—procedure and is, therefore, appropriate for particles having a diameter > 1-0.5 pm (Figure 3.5). 

The classification of wastewater in terms of size distribution is normally done from a practical point of view. Typically, a distinction is made between soluble, colloidal and suspended components (Figure 3.6). While this definition for determining what solids are is rational as far as physical transport processes in sewers are concerned, when dealing with the microbial processes for sewer conditions, an extension of the solids definition is required. Particles larger than about 10-4 pm cannot be transported through the cell wall and are, therefore, from a microbial point of view, considered particles. 

The humic/organic matter coatings of different solid phases (i. e., SPm /SP0M), such as soils, sediments, suspended solids, colloids, and biocolloids/biosolids, interact with organic pollutants in aqueous systems in various ways. Adsorption is an important interaction mode. The reversibility and/or irreversibility of the adsorption processes is of major importance. The question whether the bound residues of pollutants are to be considered definitely inactivated has been the focus of extensive research. This question was posed as follows. Have the adsorbed pollutants become common components incorporated into the humic polymer coating of solid phases (i. e., being absorbed), or are they only momentarily inactivated in reversibly bound forms thus representing a possible source of pollution by a time-delayed release of toxic units ... 

G Mechanism of Detonation in Slurries Before proceeding with a discussion of the detonation mechanism of Slurries, we need to examine briefly the rheology (flow characteristics) of SE and SBA. Any Slurry, whether expl or not, by definition contains suspended solid particles in a continuous liq phase. This liq phase in SE or SBA may be 1) an unthickened AN (and other oxidizer or even sensitizer) soln 2) a thickened soln and 3) a thickened and cross-linked soln. The thickened and/or cross-linked liq phase is a gel. An analogy supplied by Cook (Ref 9, p 277) is that pure... 

Water streams seldom consist of a single component. It may also contain two or more phases (a dissolved gas and/or suspended solids), or a mixture of one or more solutes. For mixtures of substances, it is convenient to express compositions in mole fractions or mass fractions. The following definitions are often used to represent the composition of component A in a mixture of components ... 

When a solid such as charcoal is exposed in a closed space to a gas or vapour at some definite pressure, the solid begins to adsorb the gas and (if the solid is suspended, for example, on a spring balance) by an increase in the weight of the solid and a decrease in the pressure of the gas. After a time the pressure becomes constant at the value p, say, and correspondingly the weight ceases to increase any further. The amount of gas thus adsorbed can be calculated from the fall in pressure by application of the gas laws if the volumes of the vessel and of the solid are known or it can be determined directly as the increase in weight of the solid in the case where the spring balance is used. 

Discussion. The turbidity of a dilute barium sulphate suspension is difficult to reproduce it is therefore essential to adhere rigidly to the experimental procedure detailed below. The velocity of the precipitation, as well as the concentration of the reactants, must be controlled by adding (after all the other components are present) pure solid barium chloride of definite grain size. The rate of solution of the barium chloride controls the velocity of the reaction. Sodium chloride and hydrochloric acid are added before the precipitation in order to inhibit the growth of microcrystals of barium sulphate the optimum pH is maintained and minimises the effect of variable amounts of other electrolytes present in the sample upon the size of the suspended barium sulphate particles. A glycerol-ethanol solution helps to stabilise the turbidity. The reaction vessel is shaken gently in order to obtain a uniform particle size each vessel should be shaken at the same rate and the same number of times. The unknown must be treated exactly like the standard solution. The interval between the time of precipitation and measurement must be kept constant. 

This result can also be applied directly to coarse particle swarms. For fine particle systems, the suspending fluid properties are assumed to be modified by the fines in suspension, which necessitates modifying the fluid properties in the definitions of the Reynolds and Archimedes numbers accordingly. Furthermore, because the particle drag is a direct function of the local relative velocity between the fluid and the solid (the interstitial relative velocity, Fr), it is this velocity that must be used in the drag equations (e.g., the modified Dallavalle equation). Since Vr = Vs/(1 — Reynolds number and drag coefficient for the suspension (e.g., the particle swarm ) are (after Barnea and Mizrahi, 1973) ... 

A gas suspended in a solid is also called a foam. This form of colloid is relatively rare in nature, unless we stretch our definition of solid to include rock, in which case pumice stone is a colloidal foam. Synthetic foams are essential for making cushions and pillows. There is also presently much research into forming metal foams, which have an amazingly low density. 

The clay fraction, which has long been considered as a very important and chemically active component of most solid surfaces (i.e., soil, sediment, and suspended matter) has both textural and mineral definitions [22]. In its textural definition, clay generally is the mineral fraction of the solids which is smaller than about 0.002 mm in diameter. The small size of clay particles imparts a large surface area for a given mass of material. This large surface area of the clay textural fraction in the solids defines its importance in processes involving interfacial phenomena such as sorption/desorption or surface catalysis [ 17,23]. In its mineral definition, clay is composed of secondary minerals such as layered silicates with various oxides. Layer silicates are perhaps the most important component of the clay mineral fraction. Figure 2 shows structural examples of the common clay solid phase minerals. 

Additive, exhibiting surface activity, that is added to a suspending medium to promote uniform and maximum separation of extremely fine solid particles, often of colloidal size (see Note 2 in Definition 1.39)... 

Aerosols are defined as relatively stable suspensions of solid or liquid particles in a gas. Thus aerosols differ from particles in that an aerosol includes both the particles and the gas in which they are suspended. However, while this is the rigorous definition of aerosols, one should note that the term is often used in the atmospheric chemistry literature to denote just the particles. 

As homogeneous suspension in nonaerated stirred vessels can hardly be achieved, even with very high stirrer speeds, mainly Nc, needed for complete suspension, is of interest for the design purposes. This value, by definition, is characterized by the just-suspended criterion, i.e., the state where only a small fraction of the solids remains at the bottom of the reactor for one second at maximum (Einenkel, 1979). Zwietering (1958) proposed the following correlation to predict Nc, the minimum rotational speed of agitation required for the complete suspension ... 

In an emulsion, the particles of the internal phase are spherical or liquid droplets that are dispersed throughout a liquid external phase. Even though the particles may be liquid only at elevated temperatures (50-80° C) and semisolid or rigid at room temperature, as long as they appear spherical on careful microscopic examination, they are generally considered to be emulsified rather than suspended. Thus, a clue to the presence of a suspended particle is its lack of sphericity or its definitive lattice structure. Exceptions to this general rule are spherical microspheres and related spherical solid microparticles. 

Chapter 1 (Photochromic Polymers). Like most chemical reactions, photochromic reactions are influenced significantly by the media in which they occur. This chapter surveys the interactions between photochromic entities and polymer matrices in which they are incorporated either by binding them covalently to polymer backbones or by dissolving or suspending them in polymer solids. Polymeric materials play a very crucial role in studies on photochromism, particularly from a practical viewpoint since the various applications of photochromic materials invariably require that they possess definite forms like films, sheets, plates, fibers, beads, and so on, depending on the application. 

Salinity can be represented in several ways. One of the simplest ways to quantify salinity is to use total dissolved solids (often abbreviated TDS). TDS is the total mass content of dissolved ions and molecules or suspended microgranules in a liquid medium. Generally, the operational definition is that the solids must be small enough to survive filtration through a sieve size of two micrometers. Because sodium chloride (NaCl) is the main salt in saline water, we commonly use the mass of sodium chloride as the salinity. The common units are ppm or wt.%. Of course, we can almost always use meq/mL. 

The many words employed to describe particulate systems attest to their ubiquity and to ilie impression they have made on humans from early times. Smoke, dust, haze, fume, mist, and soot are all terms in common use with somewhat different popular meanings. Thus dust usually refers to solid particles produced by disintegration processes, while smoke i nd fume particles are generally smaller and formed from the gas phase. Af/.vr.v are composed of liquid droplets. Soot usually refers to small carbon particles generated in fuel combu.stton but is now frequently used to describe very fine solid particles of silica and other inorganic oxides generated intentionally in industrial processes. In this text, however, we will rarely employ these special terms because of the difficulty of exact definition and the complexity of many real systems composed of mixtures of particles. Instead, we employ the generic term aeiosol to describe all such sy.siems of small particles suspended in air or another gas. 

The just-suspended state is defined as the condition where no particle remains on the bottom of the vessel (or upper surface of the liquid) for longer than 1 to 2 s. At just-suspended conditions, all solids are in motion, but their concentration in the vessel is not uniform. There is no solid buildup in comers or behind baffles. This condition is ideal for many mass- and heat-transfer operations, including chemical reactions and dissolution of solids. At jnst-snspended conditions, the slip velocity is high, and this leads to good mass/heat-transfer rates. The precise definition of the just-suspended condition coupled with the ability to observe movement using glass or transparent tank bottoms has enabled consistent data to be collected. These data have helped with the development of reliable, semi-empirical models for predicting the just-suspended speed. Complete suspension refers to nearly complete nniformity. Power requirement for the just-suspended condition is mnch lower than for complete snspension. 

ThLppjeesence of the solid phase will prevent the supercooling of a liquid (hence the ef cacy of inoculation or seeding ) and the presence of fh. .vapour phase will prevent the superheating of a liquid. Suspended transformation takes place more readily in the case of the passage of an isotropic into an anisotropic phase e.g. liquid into crystalline solid), where a definite arrangement of the molecules in a space lattice is necessary, than in the case of the transformation of one isotropic phase into another isotropic phase, where the molecules are in disarray. 

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