Filtration diatomaceous earth

R. Patel and D. Clifford, Radium Removalfrom Water by Manganese Dioxide Adsorption and Diatomaceous Earth Filtration, NTIS PB92-115260/AS, Springfield, Va., 1992. 

In diatomaceous-earth filtration, the powdered filter aid is built upon a relatively loose septum to screen out suspended soHds. The filter becomes clogged, and pressure losses become excessive backwashing is then necessary. The smallest removable particle is 0.5—1 p.m (see Diatomite). 

Oil Expressed as oil or chloroform extractable matter, ppmw Scale, sludge and foaming in boilers impedes heat exchange undesirable In most processes Baffle separators, strainers, coagulation and filtration, diatomaceous earth filtration... 

The pure product is produced by dissolving the gum from the seeds in hot water. Diatomaceous earth filtration is then used to purify the solution. As the gum is less soluble in alcoholic than aqueous solutions it is precipitated by adding propan-2-ol. The pressed filter cake is then washed in pure alcohol to dehydrate it. The alcohol is then recovered by pressing again. The pressed product is then milled to the required final size. 

Food and beverage processing represents an expanding area for process-scale microfiltration. Already in place are clarification systems for wine and beer, sugar, and gelatin, replacing existing practices such as diatomaceous earth filtration. Less attractive economically are miscellaneous waste treatment applications, for which microfiltration is often a sophisticated but expensive alternative. 

Centrifuging is used quite commonly in the North Coast to clarify white wines after fermentation. While it will not clarify as well as diatomaceous earth filtration, the centrifuge will handle and clarify wines of higher turbidity than the diatomaceous earth filter and, therefore, can be used immediately after fermentation. 

Sweet white wines, however, are subject to refermentation in contact with yeast. Protection from refermentation includes a combination of three factors chilling (2°-10° C), S02 (25-35 mg/L free), and reduction of yeast population to a minimum level by pad or tight diatomaceous earth filtration. At bottling, yeasts are 100 percent removed from the wine to prevent refermentation in the bottle. 

Filtration. Filtration in Washington wineries is performed almost exclusively with plate-and-frame filter presses. In some cases, these filters have wide frames so that they are capable of performing diatomaceous earth filtrations. There is only one stainless steel, screened, diatomaceous earth, pressure-leaf filter in use in the Washington wine industry. Two major wineries have found they can utilize a paper septum over a medium pad in their plate-and-frame filters. This allows them to precoat and body feed with diatomaceous earth as the wine is filtered. This accomplishes both a coarse and medium filtration in one movement of the wine. 

PRECOAT FILTRATION - DIATOMACEOUS EARTH FILTRATION. The mOSt economical method of filtering fruit juices with a high suspended solids content is with precoat filters. In these, the filter sheet is created by precoating a liquid-permeable filtering element with the filter aid. In addition to diatomaceous earth, perlite and cellulose are also used as filter aids in fruit juice production. 

FIGURE 14.11 Diatomaceous earth filtration (SURPRA disc by Pall). 

Diatomaceous Earth Filtration System Design Diatomaceous Earth Filtration System Operation Diatomaceous Earth Filtration System Maintenance Types of Precoat Filters Auxiliary Parts and Equipment Bulk Filter Aid Handling... 

Glossary of Diatomaceous Earth Filtration (Precoat Filtration)... 

Diatomaceous earth filtration (or precoat filtration), accomplishes particle removal by physically straining the solids out of the water. The thickness of the initial layer of diatomaceous earth (DE) filter medium is normally about 1/8-in. (3 mm), and the water... 

Diatomaceous earth filtration, also known as precoat filtration or diatomite filtration, relies on a layer of diatomaceous earth about 0.3-cm (1/8-in.) thick placed on a septum or filter element. The septums may be placed in pressure vessels or operated under vacuum in open vessels. A schematic diagram of a typical pressure system is shown in Fig. 2. 

Capital and Operation and Maintenance Costs of Diatomaceous Earth Filtration for Water Treatment... 

Diatomaceous earth filtration is a well-established water treatment process. It performs well on groundwater with high concentration of iron and manganese, or on surface waters with low influent turbidity, acceptable color, and bacteria levels. Effective removals of viruses and Giardia range up to 99.95% and from 99% to 99.99%, respectively. 

Comparison of Diatomaceous Earth Filtration with Other Filtration Processes... 

Diatomaceous earth filtration Established Mostly small Limited applicability potentially expensive for small systems... 

Conventinal filtration Direct filtration Slow sand filtration Package plant filtration Diatomaceous earth filtration Membrane filtration (reverse osmosis)... 

Diatomaceous earth filtration systems have been successfully adopted by the US Army for both potable water supply and wastewater treatment in the battle field since 1970s (7-9,15,16). 

GLOSSARY OF DIATOMACEOUS EARTH FILTRATION (PRECOAT FILTRATION) (1,5)... 

Dissolved Solids Any solid material that will dissolve in the liquid that is being filtered, such as sugar in water. Diatomaceous earth filtration does not remove these solids. 

G. P. Fulton, Diatomaceous Earth Filtration for Safe Drinking Water, American Society of Civil Engineers, Reston, VA, 2000. 

P. F. Schuler, M. M. Gosh, and S. N. Boutros, Comparing the removal of Giardia and Cryptosporidium using slow sand and diatomaceous earth filtration. Proceedings of 1988 AWWA Conference, Denver, CO, 1988, pp. 789-805. 

V. Bhardwaj and M. J. Mirliss, Diatomaceous Earth Filtration for Drinking Water, National Drinking Water Clearinghouse, West Virginia University, Morgantown, WV, 2001. 

Conventional treatment, which includes coagulation, flocculation, clarification (sedimentation or flotation), and filtration, along with disinfection, can achieve 99.9% inactivation of Giardia cysts and 99.99% inactivation of enteric viruses when properly designed and operated. Direct filtration, slow sand filtration, and diatomaceous earth filtration systems, each combined with disinfection, have also achieved these reductions. 

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