Fine sand

Flocculation is accelerated and higher overflow rates are achieved by external or internal recirculation of settled soflds into the feed which leads to the collection of fine particles by interception. Addition of conditioned fine sand to the feed induces separation by differential sedimentation, and sometimes increases overflow rates to 6—8 m/h. 

Finely ground cements often called ultrafine cements, having particles less than 10 p.m and an average size of 4 pm are used to grout soils with fine pore spaces, such as fine sand with a permeabiUty of lO " cm/s. These cements can be made with a wide combination of Pordand cement, slag, or siUca fume (72). 

Filter aids should have low bulk density to minimize settling and aid good distribution on a filter-medium surface that may not be horizontal. They should also be porous and capable of forming a porous cake to minimize flow resistance, and they must be chemically inert to the filtrate. These characteristics are all found in the two most popular commercial filter aids diatomaceous silica (also called diatomite, or diatomaceous earth), which is an almost pure silica prepared from deposits of diatom skeletons and expanded perhte, particles of puffed lava that are principally aluminum alkali siheate. Cellulosic fibers (ground wood pulp) are sometimes used when siliceous materials cannot be used but are much more compressible. The use of other less effective aids (e.g., carbon and gypsum) may be justified in special cases. Sometimes a combination or carbon and diatomaceous silica permits adsorption in addition to filter-aid performance. Various other materials, such as salt, fine sand, starch, and precipitated calcium carbonate, are employed in specific industries where they represent either waste material or inexpensive alternatives to conventional filter aids. 

FIG. 19-28 D( istcr-Ov( rstroi)i diagonal deck talilc. Center, diagonal deck with pool riffle systein for sand liottoin, diagonal deck with pool riffle system for fine sand and slime. 

As described in the previous section, casting dispersions based on monomer and fine sand ru e now finding use in high-grade sanitary ware and tiling. 

Gravel Coarse sand Fine sand Silt... 

The hydraulic performances required of the sand with slow filters are inferior to those for rapid filters. In the case of slow filters, one can use fine sand, since the average filtration velocity that is usually necessary lies in the range 2 to 5 m/day. 

For new installations the first washing cycles result in the removal of fine sand as well as all the other materials usually undesirable in the filter mass, such as... 

Staub-luft, /. dust-laden air. -maske, /. dust mask, -mehl, n. (fiom) mill dust, dustings, -ol, n. fioor oil. -sand, m. very fine sand, sand dust, -sauger, m. dust suction apparatus, vacuum cleaner, -schutzmaske, /. dust mask. 

The normally good lubricating qualities of mud can be lost if cuttings, particularly fine sand, are not effectively separated from the mud. Adequate settling pits and shale shakers usually eliminate this trouble. Desanders are used occasionally. 

Solvent-free high-build floor paints are available which can be readily applied with brush, roller or spray to a prepared concrete substrate to give a thickness of 0.10-0.20 mm per coat. Normally, two coats are applied and the first is often lightly dressed with fine sand or carborundum dust to give a non-slip, chemically resistant and durable colored floor, ideal for light industrial traffic conditions (for example, rubber-shod wheels). ... 

The effects of different types of sand on the corrosion of mild steel have been studied in the laboratory. It was concluded that fine sand has a higher salt content and is more corrosive than coarse sand within the partical size range < 0-25-2-4mm. 

The tapes are usually relatively thin (0-5 mm) and easily damaged. It is, therefore, essential to take elaborate precautions to provide physical protection to the tape once it has been applied both during construction and after burial. Good results have been obtained when the tape is applied by line travelling machine and without further handling, immediately lowered into a sand padded trench and covered over with fine sand before the trench is back filled. 

Soda ash, slaked lime, limestone, or sodium bicarbonate. Cover spills with vermiculite, diatomaceous earth, clay, or fine sand followed by one of the decontaminants. 

Spent foundry sand is thought of as a beneficial substitute for fine sand for use in portland cement concrete. Prior to acceptance of inclusion, test standards applied on conventional fine sand shall be referred to as the standards for spent foundry sand to compare the physical properties of conventional sand and spent foundry sand. The most important parameters are particle size distribution, fineness modulus, dust content, density, organics content, deleterious materials content, and grain shape. Although no spent foundry sand satisfies all of the specifications, foundry sand can be blended with conventional sand to be incorporated into the concrete matrix. The replacing ratio normally starts at one-third. 

Granular bed filters are used in porcelain enameling wastewater treatment to remove residual solids from clarifier effluent (sedimentation effluent or flotation effluent). Filtration polishes the effluent and reduces suspended solids and insoluble precipitated metals to very low levels. Fine sand and coal are media commonly utilized in granular bed filtration. The filter is backwashed after becoming loaded with solids and the backwash is returned to the treatment plant influent for removal of solids in the clarification step.10-12... 

Wind transport. Wind-blown components are carried away over a more or less important distance as a function of wind velocity and particle size of the material. Wind speeds up till 6.5 m/sec transport dust and fine sand with a diameter of less than 0.25 mm sand grains up to 1 mm diameter are uplifted at wind speeds of 10 m/sec. At 20 m/sec also particles of 4-5 mm may be removed. Based on these physical laws, the transportation of coarse fragments, in casu the sand fraction, occurs over-relatively short distances from the deflation zones. These sand grains settle then in more or less continuous layers and either become progressively mixed with the underlying soil layers, or concentrate in dune formations. 

Barley leaves Winchester fine sand 0.0038 Rediske et al. (1955)... 

Hammons, R.H. 1977. Atrazine Persistence in a Valentine Loamy Fine Sand Profile. M.S. Thesis. Univ. Nebraska, Lincoln. 48 pp. 

ACTIFLOW A process for treating raw water. Flocculation of insoluble matter by the addition of a polyelectrolyte takes place within an agitated bed of fine sand. Developed in France by OTV and licensed in the UK through General Water Processes. 

Fig. 2. Solid-phase arsenic in ppm versus depth in m from a continuous core. The core consists of clayey silt to depth of 28 m, and fine sand thereafter with a silt horizon at 34 m depth. As was measured by digestion with an HCI-HNO3-H2O aqua regia solution followed by inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectroscopy analysis.

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