Removal odor compounds

Table 12.9-3 summarizes the results of the VOC removal and remediation tests conducted on the Prototype Unit. The results indicate that better than 75 % per pass reduction can be obtained for VOC level less than 50 ppm. At least 50 % reduction is obtained for concentrated VOC (> 50 ppm) airstream. The conversion rate depends on the VOC and its concentration. The Prototype Unit is very effective in removing odorous compounds such as Chinese incense and air freshener used in most Hong Kong household. 

Cmde oils from these processes are often of insufficient quaUty to be used directly, particularly for edible products. Impurities such as pigments, phosphatides, volatile odorous compounds, and certain metals must be removed by further processing. 

The most common application of carbon adsorption in municipal water treatment is in the removal of taste and odor compounds. Figure 12 provides an example of a process flow diagram for a municipal water treatment plant. In this example water is pumped from the river into a flotation unit, which is used for the removal of suspended solids such as algae and particulate matter. Dissolved air is the injected under pressure into the basin. This action creates microbubbles which become attached to the suspended solids, causing them to float. This results in a layer of suspended solids on the surface of the water, which is removed using a mechanical skimming technique. Go back to Chapter 8 if you need to refresh your memory on air flotation systems. 

Spent caustic solutions from petroleum refining. Petrochemical refineries use caustics to remove acidic compounds such as mercaptans from liquid petroleum streams to reduce produced odor and corrosivity as well as to meet product sulfur specifications. Spent liquid treating caustics from petroleum refineries are excluded from the definition of solid waste if they are used as a feedstock in the manufacture of napthenic and cresylic acid products. U.S. EPA believes that spent caustic, when used in this manner, is a valuable commercial feedstock in the production of these particular products, and is therefore eligible for exclusion. 

Odor evaluation, in perfumes, 18 379 Odor impacts, air pollution dispersion modeling for, 26 725 Odorous compounds controlling, 10 75 in wastewater, 26 723t Odor panels, 26 724 Odor pollution, 26 669 Odor removal, adsorbents for, 1 611 Odors... 

Glaze W H, Schep R, Chauncey W, Ruth E C, Zarnoch J J, Aieta E M, Tate C H, Me Guire M J (1990) Evaluating Oxidants for the Removal of Model Taste and Odor Compounds from a Municipal Water Supply, Journal of American Water Works Association 5 79-83. 

The need to remove sulfur compounds from petroleum arises not only from the objectionable odor that the thiols impart to petroleum products but also from the instability which sulfur compounds appear to promote in petroleum products. For example, free sulfur, which can be formed in a product by the oxidation of hydrogen sulfide ... 

Before the naphtha is redistilled into a number of fractions with boiling ranges suitable for aliphatic solvents, the naphthas are usually treated to remove sulfur compounds, as well as aromatic hydrocarbons, which are present in sufficient quantity to cause an odor. Aliphatic solvents that are specially treated to remove aromatic hydrocarbons are known as deodorized solvents. Odorless solvent is the name given to heavy alkylate used as an aliphatic solvent, which is a by-product in the manufacture of aviation alkylate. 

Coconut shell is the source of two other products, coconut shell flour and activated charcoal. Powdered coconut shell is used in the plastics industry as a compound filler for synthetic resin glues. It is also used as a filler and extender of phenolic molding powders that give a smooth and lustrous finish to molded articles, thereby improving their resistance to moisture and heat. Activated charcoal is an adsorbent for toxic agents. It has been used in gas masks, but can also be used to remove odors and industrial stench. As well, this by-product is a contact catalyst used to facilitate some industrial chemical reactions (61). 

Although the process is commonly named deodorization, it is actually a combination of three different effects on the oil (1) stripping Stripping of volatile components (free fatty acids, odorous compounds, tocopherols, sterols, and contaminants such as pesticides and light polycyclic aromatic hydrocarbons, etc.), (2) actual deodorization Removal of different off-flavors, and (3) temperature effect Thermal destruction of pigments and unwanted side reactions such as cis-trans-iso-merization, polymerization, conjugation, and so on. 

Deodorizing is generally conducted to remove odors, peroxides, and other compounds from the bleached oil. In some cases, this step is used to remove free fatty acids as well in which case, it becomes a physical refining operation. If the starting oil is of good quality, the neutralization step with caustic solution may be avoided, and the deodorizer can be used also as a physical refiner. Deodorization is usually done by injecting pure steam into the heated oil (300-450°F) under high vacuum (0.002 mm Hg). 

Permanganate taste/odor compounds Also for iron and manganese removal Often complemented by carbon adsorption Easy to feed/monitor Production of hydrous Mn02 has been shown to adsorb some toxic organic cmpds moving trace amounts of organic compounds equipment... 

This paper will consider the efficacy or horse-radish peroxidase (HPR) for the removal of 2-chlorophenol — a taste and odor compound, and pentachlorophenol — a wood preservative sometimes found as a contaminant in drinking-water. These compounds were evaluated at low as well as high concentrations, and in the presence of potential competing compounds. Competing compounds may be innocuous aromatic compounds or other specific micro pollutants. Humic substances are organic compounds composed mainly of aromatic structures [ 14 ] which account for up to 90% of the background total organic carbon (TOC) in natural waters [15 ]. Recent studies have indicated th t the presence of humic acids may deactivate horse-radish peroxidase [16 ]. 

The use of enzymes in drinking-water treatment has several advantages over the use of whole bacteria. Enzymes often have high specificities for substrate, so there is better control over the compound removed and the product produced. The enzyme concentration in the water is controlled by the plant operator. Thus there is no dependence on the growth rate of the bacteria. This can be particularly important when the compound targeted for removal appears only sporadically in the raw water, such as taste and odor compounds. Bacteria require an incubation time to acclimate to the substrate and grow, but enzymes may be added as needs require. 

The advantage of steam distillation over other methods of volatile oil extraction lies principally in its wide applicability and speed of operation. Most plants or plant parts, with the exception of the flowers in some few cases, may be extracted most readily and most expeditiously and with a minimum amount of labor by the steam distillation method. The simplicity of the operation is obvious. The removal of the oil is much more complete than by any other process. Furthermore, there is produced as a by-product during the distillation an aqueous distillate which is completely saturated with the oil. The aqueous distillate may in many instances be utilized and sold as an aromatic water of commerce, especially in such cases as lavender, orange flowers, rose, etc. The aromatic waters possess excellent odors, largely because of the extreme dilution of the odorous compounds held in solution, and are useful in the perfumery and toilet-preparation industries. When the aqueous distillate from the plant has no marketable value, it may be profitably collected and returned to the boiler. In case of a further distillation of the same plant it will materially add to the yield of oil, since the distillate is a saturated solution of the oil. Many oils are extremely soluble in water. Distillates from oils of this class usually augment considerably the yield of oil when returned to the boiler and transformed into steam and oil vapors. 

However, tools such as these can be used successfully to compare the performance of different activated carbons and to give an indication of the expected lifetime of the filters, and therefore provide a caution to water authorities when increased monitoring of filter effluent water quality might be warranted. Another type of test, the mini-column test, was used successfully by Gillogly et al. [17] to simulate the removal of the musty odor compound MIB in a phot-scale GAC filter over a period of several years. This simple test, described in more detail in a later section, cannot be used to predict the lifetime of a GAC filter, but it can indicate how well a filter would function at the time of sampling if challenged by an unexpected microcontaminant influx. Thus predictive tools such as SBA or RSSCT can be used in conjunction with a monitoring tool, such as the minicolumn test, to allow the confident use of GAC for the removal of problem compounds. 

The practical application of PAC for the removal of MIB and geosmin has been aided by the application of the HSDM [63, 64, 68]. Figure 26.8 illustrates the difference in the adsorption of the two compounds, and the fit that the HSDM can give to the data. Diffusion coefficients derived from these fits can then be used to predict the adsorption of the taste and odor compounds, and consequently the PAC doses required under particular water treatment plant situations [63, 68, 69]. 

The Lyonnaise des Eaux in France [4.116] has developed a process for the denitrification of underground waters in order to produce drinking water. This process combines a bioreactor with adsorption by powdered activated carbon, together with a hollow-fiber UF unit. This process allows the elimination of nitrates, nitrites, pesticides, and herbicides (atrazine, diethylatrazine, simazine, metabenzthiazuron, and urea derivatives, etc.) as well as taste and odor compounds. These molecules are frequently present in underground waters in Europe, as a result of past intensive agricultural practices. The UF membrane unit also disinfects the water by removing protozoa, bacteria, and viruses. 

Partial proteolysis of soybean proteins with endopeptidases has been used to remove flavor compounds and related fatty materials from soybean curd and defatted soybean flour (21). Certain soybean protein concentrates possess an undesirable beany and oxidized flavor. Treatment of soybean curd and defatted soybean flour with endopeptidases such as aspergillopeptidase A released off-flavor compounds such as 1-hexanal and 1-hexanol which could be removed from the hydrolysate by solvent extraction. The enzymically digested products had less odor, taste, and color than the starting material and were more stable to oxidative deterioration. 

Deodorants and antiperspirants are ftequendy compounded together. Deodorants seldom actually remove odor they simply mask odors or inhibit the microorganisms that cause body odor. Deodorants include several strong perfumes, often with minty or musky odors. Odors can be lessened somewhat by decreasing perspiration. Most underarm perspiration comes from the apocrine or eccrine glands. Perspiration probably functions primarily to cool the skin and get rid of excess heat, but may also carry pheromones and fatty acids and excrete excess salt. The active ingredients of antiperspirants are usually aluminum salts such as aluminum chloride (AlCft). Aluminum ions are absorbed by cells in the epidermis that squeeze the sweat gland ducts closed. Talcum powders may be used to absorb excess perspiration. 

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