Oil globules

Low concentrations of oil can be removed by dissolved air flotation (DAF). In this process, an effluent recycle is pressurized in the presence of excess air, causing additional air to go into solution, in accordance with Henry s Law. When this water is discharged to the inlet chamber of the flotation unit at close to atmospheric pressure, the dissolved air comes out of solution in the form of tiny air bubbles which attach themselves to and become enmeshed in suspended solids and oil globules. The primary design criteria is the air/solids ratio, which is defined as the mass of air released divided by the mass of solids fed. Sufficient air must be released to capture the solids in the influent wastewater. The performance of DAF for the treatment of several... 

A, discoloured, oil-depleted, aqueous phase B, oil globule-rich creamed layer, C, coalesced oil layer limi cracked emulsion D, liingal mycelial growth on surface. Also present are a foul taste and evil smell ... 

Since a-tocopherol destroys nitrite in the system in absence of the oil phase, we may postulate that the ineffectiveness of these two oil soluble inhibitors resulted from their absence from the aqueous phase. Diethanolamine is miscible with water and presumably its nitrosation occurs in the aqueous phase. There is a significant difference in the solubility characteristics of ascorbyl palmitate. The reducing portion of the molecule is water soluble. Thus the ascorbate moiety may be in the aqueous phase while the fatty acid tails may lie within the oil globules. The a-tocopherol and the BHA may well be effective if they are dispersed in the aqueous phase after preparation of the emulsion. This will be investigated in future experiments. 

After allowing the emulsion to stand for a time the drop number was taken, the assumption being made that the oil globules would have no effect. The figures were —... 

A serious discrepancy was found between the experimental and the calculated values of , the former being 20—30 times greater than the latter. This is no doubt due in part to the experimental errors involved in the method, inasmuch as the size of the oil globules in the emulsion varies considerably and it is therefore difficult to obtain a reliable value for the radius, and consequently for the total active surface. 

Figure 6.2 represents the behavior of quasi-monodisperse double emulsions in (C , (pf) coordinates, where (pf is the initial volume fraction of droplets in the globules. Sorbitan monooleate (SMO) was used for the stabilization of the primary W/O emulsion and sodium dodecyl sulfate (SDS, CMC = 8 10 mol/1) was used for the stabilization of the oil globules in the external aqueous phase. Three different compositions zones, referred to as A, B, and C can be defined they differ by their qualitative behavior observed via microscopy. Moderate internal droplet volume fractions are considered first (cpf < 20%). If Ck = CMC/10, the system does not exhibit any structural evolution after a few days of storage (zone A). If C is... 

In the absence of coalescence, the global molecular flow 7 of a species across the oil globules is entropic in origin and is described by Eick s law ... 

The process involves removal of materials less dense than water (such as oil) and suspended materials that are more dense than water by settling. The API separator does not separate substances in solution, nor does it break emulsions. The effectiveness of a separator depends on the temperature of the water, the density and size of the oil globules, and the amounts and characteristics of the suspended materials. The susceptibility to separation (STS) test is normally used as a guide to determine what portion of the influent to a separator is amenable to gravity separation [38]. In terms of globule size, an API separator is effective down to globule diameters of 0.015 cm (15 microns). 

Owing to its film forming properties Acacia gum must cover perfectly each oil globule with a colloidal film. 

As Acacia gum emits negative charges around the circumference of its molecule, electric repulsion will occur between each oil globule so that coalescence is prevented. The oil globule must be neither too small as this would cause the globules to agglomerate nor too large (immediate rise). 

One of the major focuses of the in situ use of surfactants is to accelerate the removal or degradation of free-phase products (DNAPL or oil globules) as variations of technologies used in the oil industry for enhanced tertiary oil recovery as described by Hill et al. (1973)- Such in situ remediation efforts often fail, however, primarily because of differences in the goals and expectations of the applications. For example, the enhanced oil recovery industry is often satisfied with > 30% enhanced removal whereas the remediation industry often strives for >99% removal in order to meet remedial guidelines. Unfortunately, removal of about 50% of the free product (i.e., DNAPL) at a PAH-contaminated site appears to represent the full extent of practical field expectations. 

The API separator is basically one or more long channels with a maximum flow area and minimum depth. This minimizes turbulence and allows oil globules greater than 0.U06 in (0.15 mm) in diameter to nse to the surface. where they are skimmed off. This type of vessel was attractive because it was simple and effective, and could he sized to neat specific intlow rales... 

Oil waicr separation should occur primarily in the flow channel between the two spreaders. As a result, oil will build up in the space below the upper spreader and above the top of the upper slots. Although this oil blanket will help small oil globules to coalesce and move out of the flowstream, it could become contaminated with anaerobic bacteria, w hich would be a source of corrosion. This can be minimized by treating the inlet stream with a bactericide at regular intervals. Secondary oil/water separation will occur in the region outside the spreaders and in the area below the lower spreader. Secondary separation also will occur in the quiet space between the upper spreader and the oil/water interface... 

Vertical-Tube Coalescer This is the equipment finally selected to meet the design parameters listed in Table 2. The vertical-tube coalescer (VTC) unit equals the performance of a skimmer in less space or offers improved performance in the same space. The VTC tube packs provide up to five times more coalescing surface than a plate pack. The extra surface gives oil globules more area for coalescence Also, the vertical orientation of the tubes contributes to a more efficient separation. In a plate pack, the rising oil droplets must move perpendicular to the flow of influent. In a VTC pack, the oil droplets arc free to travel upward and to collect on the top surface of the tube bundles. 

Identification When examined under a microscope, a sample exhibits numerous irregular masses and isolated yeast cells—the latter ovate, elliptical, spheroidal, or elliptic-elongate in shape, some with one or more attached buds—up to 12 pun in length and up to 7.5 xm in width. Each has a wall of cellulose surrounding a protoplast containing refractile glycogen vacuoles and oil globules. 

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