Clarification by filtration

Fig. 11. Flow chart of a typical pDNA production process. After fermentation cells are harvested and lysed by addition of alkaline solution. Clarification by filtration is followed by a series of chromatographic steps. After a final 0.22 pm filtration step the purified plasmid is aliquoted and stored...

Solvent Extraction Experiments. Solvent extraction studies were done on two feed samples representing dissolved hydroxide cake (SSA) and evaporator supernate (SSB). SSA was prepared by dissolution of hydroxide cake with slow addition of concentrated HN03, adjustment of the final acidity to 0.5 N by addition of water and/or HN03, and clarification by filtration. To prepare SSB, some supernate liquid from the evaporator was titrated, acidity adjusted to 0.5 N by NaOH and water addition, then clarified by filtration. No appreciable solids were observed on the clarification filters for either solution. Compositions of these feeds are listed in Table III. 

Other than the fiber aid, to form a highly porous and uniform filter cake. The suqiension to be filtered is then introduced onto the filter. Clarification by filtration results by the action of the filter aid trapping the suspended solids within the filter aid cake, by the techniques described in Section 6.1. Only a thin layer of cake is usually considered to be inq>ortant in this operation. If the filtration equipment is continuous by nature, e.g. a rotary vacuiuu filter, a thick filter aid cake may be enployed as the top layer contaminated with the material filtered during the clarification can be scraped off and discarded. The layers below the surface are then exposed for fiuther filtration and, therefore, economically viable rates of filtration ensue. Alternatively, if the filtration is conducted in a batch vessel thinner filter aid cakes are usually employed, with more frequent cleaning required. 

The more usual and obvious remedy is clarification by filtration. 

Although it is sometimes encouraged in white wines, particularly barrel-fermented Chardonnay, this fermentation tends to lower fmitiness and be considered undesirable in other white wines unless acidity is too high. This is also tme for pink and light red wines. If it occurs after bottling, a gassy, cloudy wine results. In such wines, it can be avoided by careful attention to clarification or filtration sufficient to remove the bacteria, by adding SO2 at appropriate intervals as an inhibitor, or by pasteurization. 

In the precoat and body feed mode, filter aids allow appHcation of surface filtration to clarification of Hquids, ie, filtration of very dilute suspensions of less than 0.1% by volume, such as those normally treated by deep bed filters or centrifugal clarifiers. Filter aids are used in this mode with pressure filters. A precoat is first formed by passing a suspension of the filter aid through the filter. This is followed by filtration of the feed Hquid, which may have the filter aid mixed with it as body feed in order to improve the permeabiUty of the resulting cake. The proportion of the filter aid to be added as body feed is of the same order as the amount of contaminant soHds in the feed Hquid this limits the appHcation of such systems to low concentrations. Recovery and regeneration of filter aids from the cakes normally is not practiced except in a few very large installations where it might become economical. 

Filtration. Any type of clarification is foUowed by filtration through leaf-type vertical or horizontal pressure filters. Carbonatated Hquors, containing calcium carbonate, may require addition of diatomaceous earth as a filter precoat. Phosphatated Hquors are generally filtered with the addition of diatomaceous earth as precoat and body feed. 

Corrective Action Application An acidic groundwater at a Florida site (pH 2.5-3) required treatment. The groundwater was collected by extraction wells, pumped to an above-ground reactor, and neutralized with lime. In the course of neutralizing the waste stream, precipitates were formed which were removed by clarification and filtration prior to discharge. Sludges produced from the clarification and filtration steps were dewatered by a filter press. 

The steps involved in converting soluble hardness salts in the RW to insoluble precipitants that can be subsequently removed by filtration or clarification, are ... 

Removal of Heavy Metals from Coil Coating Wastewater by Lime Precipitation, Clarification, and Filtration... 

Optimal water management (water loop arrangement), water clarification by sedimentation, flotation or filtration techniques, and recycling of process water for different purposes. 

In addition to the heavy metals stated in Table 22.10, ferro- and ferricyanide are also part of the pollutants in the wastewater generated in a chrome pigment plant. These wastes are generally combined and treated through reduction, precipitation, equalization, and neutralization to be followed by clarification and filtration processes. Most of the heavy metals are precipitated using lime or caustic soda at specific pH. Chromium is reduced by S02 to a trivalent form, wherein it is precipitated as chromium hydroxide at specific pH. Sodium bisulfide is also employed to precipitate some of the metals at a low pH. The treated water is recycled for plant use while the sludge is sent to landfills (Figure 22.7). 

The application of ion exchangers to dextrose process liquors involved considerable experimental work because of a number of factors which do not enter into their application to water purification. The accumulation of fats and proteins on the resin surfaces must be guarded against by proper clarification of the liquors to be treated. Such accumulation may result from precipitation as the neutralization progresses, and may soon destroy the effective acid-removing capacity of the anion exchange resin. This difficulty can effectively be eliminated by prior precipitation of thfe refinery residue from the acid liquor by bentonite, a colloidal clay of opposite electrical charge to the colloids,21 followed by filtration. 

Pectinases and (3-glucanases are the only enzymes allowed in wine-making by European legislation. They are used as clarification and filtration agents and also to release aroma compounds that are mostly present in grape as nonvolatile glycosidic precursors. Pectolytic enzymes are also reported to increase extraction of phenolic compounds and wine color... 

The black deposit produced by the action of sulphuric acid, after having been heated and subjected to pressure, yields about eighty per cent, of oil, which, after clarification and filtration, is little inferior to the oil first obtained. 

The process of pretreating hard water with lime and sometimes soda as well, based on standard precipitation methods, to reduce the hardness either to a minimum level or more usually to a preset level of, say, 85 ppm, thereby lowering the total treatment costs. Usually carried out in specially designed tanks and followed by clarification and filtration. Calcium bicarbonate is always removed, requiring one equivalent... 

Vinegar clarification is accomplished by filtration, usually with the use of filter aids such as diatomaceous earth or bentonite. After clarification, vinegar is bottled, sealed tightly,... 

The sample to be analysed does not require any particular sample pre-treatment. However, in the case of musts or cloudy wines, a preliminary clarification by centrifugation or filtration is recommended in order to prevent system blockage. Carbon dioxide levels exceeding 750mg/L should be reduced or eliminated before analysis to avoid degassing of the sample in the analytical circuit. 

Another example includes the recovery (mass %) of API and degradation products of API from two 100-mg tablet (5 tablets) sample solution clarified by filtration and clarified by means of centrifugation. The data in the Table 8-5 demonstrates that the two methods of sample clarification are equivalent and that the filtration procedure (0.2-pm Nylon filter, with 5 mL pre-wet) is... 

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