Hydraulics permeability

Alternative final cover systems, such as the innovative evapotranspiration (ET) cover systems, are increasingly being considered for use at waste disposal sites, including municipal solid waste (MSW) and hazardous waste landfills when equivalent performance to conventional final cover systems can be demonstrated. Unlike conventional cover system designs that use materials with low hydraulic permeability (barrier layers) to minimize the downward migration of water from the cover to the waste (percolation), ET cover systems use water balance components to minimize percolation. These cover systems rely on the properties of soil to store water until it is either transpired through vegetation or evaporated from the soil surface. 

H Yasuda, CE Lamaze, A Peterlin. Diffusive and hydraulic permeabilities of water in water-swollen polymer membranes. J Polym Sci A-2 9 1117-1131, 1971. 

Dialysis, kidney, 15 844-845 Dialysis membrane, hydraulic permeability/ultrafiltration coefficient of, 26 818-819 Dialyzer model, 26 817 Dialyzers... 

Hydraulic permeability/ultrafiltration coefficient, of a dialysis membrane, 26 818-819... 

It is indicated that these transport parameters are functions of A. The hydraulic permeability (D Arcy coefficient), /Cp (A), exhibits strong dependence on A because larger water contents result in an increased number of pores used for water transport and better connectivity in the porous network, as well as in larger mean radii of these pores. A modification of the Hagen-Poiseuille-Kozeny equation was considered by Eikerling et aU- to account for these structural effects ... 

ORR rate constant as defined by eq 61, 1/s ORR rate constant in Figure 11, cm/s thermal conductivity of phase k, J/cm K relative hydraulic permeability saturated hydraulic permeability, cm electrokinetic permeability, cm catalyst layer thickness, cm parameter in the polarization equation (eq 20) loading of platinum, g/cm molecular weight of species i, g/mol symbol for the chemical formula of species i in phase k having charge Zi... 

For the pressure studies, two phase" compact ion behavior is observed with an inflection point between 7 and 11 atms. For the aqueous solution studies, the hydraulic permeability K and the g-ratio are hardly effected by solute type (within experimental error). The solute diffusive permeability however, varies with solute type in good qualitative agreement with free energy parameters, infrared overtone shifts, and spin echo and continuous wave nuclear magnetic resonance spectroscopy results from the literature. 

Water Transport. The dependence of the diffusive permeability of tritiated water Pq., (HTO) and hydraulic permeability LpAX on the lEC are presented in Figures 4 and 5. Both Pj and LpAX can be seen to increase exponentially as a function of lEC. Since the volume fraction of water, (J>, is also a linear function of the lEC, a similar exponential relation is obtained for these parameters vs. (J>. In terms of the pore model, the increase in either diffusion permeability or the hydraulic permeability may be caused by one or both of the following possibilities (a) an increase in the number of passageways, or (b) by increase in the radius of the pores. This question may be resolved by examining the g factor, defined as a ratio of two permeabilities (15) ... 

Figure 5. Intrinsic membrane hydraulic permeability vs. I EC (9) SPS obtained by sulfonation of P-3500 resin TXJ SPS obtained by sulfonation at P-1700 resin) ...

The coefficient of hydraulic permeability (Lp) of ozone-treated bean leaf tissue tends to decrease when measured by water loss or uptake (Fig. 6). Here, ozone-treated tissue was equilibrated with 0.2 M mannitol (approximately isotonic) immediately after exposure. The tissue was then either allowed to take up tritiated water or, after a period of tritiated water uptake, allowed to lose tritiated water into a mannitol solution. In both the influx and efflux experiments, ozone-treated tissue transported tritiated water at a lower rate than control tissue. 

Similar experiments in which tissue was allowed to hydrate or dehydrate in hypotonic or hypertonic solutions also showed a lower rate of water transport for ozone-treated tissue (13). Hence, the coefficient of hydraulic permeability (Lp) appears to be decreased by ozone exposure. 

The reabsorption of NaCl by the thick ascending limb is not accompanied by water because of the low hydraulic permeability of this nephron segment. Consequently, the tubular fluid becomes dilute as it passes through the thick ascending limbs. This process contributes to normal urinary dilution. Moreover, when Na+ transport in thick ascending limbs is inhibited, urinary dilution will diminish. 

The EiAD technology works most effectively on clay-type soils where the hydraulic permeability is small. Results indicate that the EiAD technology can remove inorganic contaminants such as zinc and cadmium from clay sods. Soil contaminants may be cations, such as cadmium, chromium, and lead, or anions, such as cyanide, chromate, and dichromate. 

Electrokinetic treatment can be used to remediate soils, sludges, and sediments contaminated with heavy metals and organic hydrocarbons. Electrokinetic treatment works well on clay-type soils with low hydraulic permeability, which are difficult to treat using other in sitn technologies. Electrokinetic permeabilities for aqueous systems in clays have been demonstrated to be up to 1000 times greater than normal hydraulic permeabilities, and some heavy metals have exhibited removal efficiencies of up to 100%. 

Lynntech, Inc. s (Lynntech s), electrokinetic remediation of contaminated soil technology is an in situ soil decontamination method that uses an electric current to transport soil contaminants. According to Lynntech, this technology uses both direct current (DC) and alternating current (AC) electrokinetic techniques (dielectrophoresis) to decontaminate soil containing heavy metals and organic contaminants. A non homogeneous electric field is applied between electrodes positioned in the soil. The field induces electrokinetic processes that cause the controlled, horizontal, and/or vertical removal of contaminants from soils of variable hydraulic permeabilities and moisture contents. 

Can treat varying soil textures (including soils with low hydraulic permeability such as clays). 

Equation (6.1.4) asserts that the volumetric flow rate is a superposition of two components. They are the electro-osmotic component proportional to the electric field intensity (voltage) with the proportionality factor u> and the filtrational Darcy s component proportional to —P with the hydraulic permeability factor i>. Teorell assumed both w and t> constant. Finally another equation, crucial for Teorell s model, was postulated for the dynamics of instantaneous electric resistance of the filter R(t). Teorell assumed a relaxation law of the type... 

Below we shall need some order of magnitude estimates for the hydraulic permeability i> and the electro-osmotic coefficient u>. Such estimates are provided by the expressions... 

The heterogeneity of porous media with respect to their hydraulic permeability poses one of the most difficult problems. This is especially true for aquifers formed by glacial and fluvial deposits. Prediction of breakthrough curves may become impossible if a few long macropores or highly conducting layers are present in which water moves at a speed 10 or 100 times faster than the effective mean velocity. Such situations are still full of surprises, even to the specialist. 

The requirement of hydrophilicity in barrier materials has been widely accepted, but the mechanism by which it affects membrane performance, especially for the permselectivity, is not fully understood. Cellulose acetate and some kinds of polyamides and their analogues featured in the present review have both hydraulic permeability and permselectivity, while most highly hydrophilic materials have high permeability for water and show unselective permeation for ions and organic solutes. 

Fig. 3. Dependence of hydraulic permeability of various membranes on their degree of hydration H at 25 °C.

The gel usually has a much lower hydraulic permeability and smaller apparent pore size than the underlying membrane. (The gel layer and the concentradon gradient between the gel layer and die bulk concentration are called the gel-polarization layer.)... 

The gel-polarization layer has an hydraulic permeability of Kg. Equation 4 states that flux is independent of pressure, and Kg must therefore decrease with increasing pressure. Equation 1 becomes... 

Staverman [165, 166) has shown how a number of transport phenomena across membranes, such as ion migration, hydraulic permeability, and membrane potentials are related to the Lilt s. In general, if there are n components, n [n— I) independent measurements are required to estimate all Lik s. So for a system consisting of 3 components (e.g. sodium ions, chlorine ions and water) 6 independent measurements are necessary. 

According to (82), Dn is the hydraulic permeability measured at solutions which have been electrically short-circuited. Generally... 

Johnson, E.M. and Deen, W.M. (1996) Hydraulic permeability of agarose gels. AlChE, 42, 1220-1224. 

Lr Membrane constant for solute transport by diffusion (m/s) Lp Membrane hydraulic permeability (mol m 2s-1bar-1)... 

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