Malodorous substances

The sewer processes take place in a complex system. They proceed in one or more of the five phases the suspended water phase, the biofilm, the sewer sediments, the sewer atmosphere and the sewer walls, and by exchange of relevant substances across the interphases. Processes that proceed in the sewer system affect other parts of the urban system, i.e., the urban atmosphere with malodorous substances. Furthermore, wastewater treatment plants and local receiving waters receive not just those substances discharged into the sewer but also products that are the result of the sewer processes (Figures 1.1 and 1.3). 

Only a few studies have been concerned with measurements of specific odorous compounds in sewer systems. Hwang et al. (1995) have analyzed the influent wastewater in a study of malodorous substances in wastewater at different steps of sewage treatment (Table 4.3). 

This extremely malodorous substance should only be prepared and used under a well-ventilated hood or in a fume chamber. In particular, the substance must not be allowed to come into contact with the hands or the clothing, since the odour clings for days. 

Lindvall, T. and Svensson, L. T. (1974). Equal unpleasantness matching of malodorous substances in a comrrtunity. Journal of Applied Psychology 59,264. 

Dimethylthietane is a component of the secretion from the anal gland of the mink (Mustek vision). the European polecat (M. putorius) and ferret. The ferret also produces cis- and trans-2,3-dimethylthietane, 2-n-propylthietane, and 2-n-pentylthietane. 2-n-propylthietane is the major malodorous substance secreted by the anal gland of the male stoat (M. erminea). The female stoat secretes 2-ethylthietane. Thietane, itself, is said to be a component of shale oil. ... 

Irritants (peripheral sensory irritants), lacrimators, sternutators, emetics, sedatives, hypnotics, serotonin antagonists, hypotensives, thermoregulator disrup-tors, nauseants, vision disruptors, neuromuscular blockers, malodorous substances, centrally acting anesthetics, immobilizers, tranquillizers. 

Gasification of Leather Offal. Chrome-leather tanning scraps or offal are a waste product of the tanning and leather industries. These wastes are usually the result of trimming operations and contain 3.5 wt % chromium and about 50 wt % water. The wastes cannot be incinerated because malodorous substances and carcinogenic chromium-containing particulates are formed. Landfill disposal is presently used. 

Contamination of persons with malodorous substances, such as mercaptans and amines, has been proposed as a means to deter less motivated rioters based on psychological and physiological effects such as olfactory repulsion and nausea (Whitten et al., 1970). They can be delivered by frangible missile, and addition of a thickening agent will prolong adhesiveness. 

Whitten, B., Wagman, W., Saffer, R., and Cohen, I., Malodorous substances as riot control and training agents, Edgewood Arsenal Technical Report Series Number 4370, Department of the Army, Edgewood Arsenal, MD, 1970. 

If the efficiency of destruction of the harmful substance is to be above 90%, then the residence time of the pollutants in the oxidation zone should be approximately 0.5 s and the temperature must not decrease below its limit value (500 to 650°C for the combustion of hydrocarbons and 750 C in the presence of carbon monoxide) and the destruction of malodorous substances require temperature above 800°C. Such thermal combustion can be employed in petroleum refining plants and in the petrochemical industry, for removing hydrocarbons from final gases, for removing vapours of solvents in the chemical and woodworking industry, and in steel works, etc. 

The main risks involved in nsing natnral cork are the leakage that can occnr if the bottles are not perfectly sealed and contamination by malodorous substances released by corks that prodnce cork taint . In France, approximately 3-4% of all bottled wine is estimated to be affected by cork taint. The organoleptic and economic harm cansed by cork taint, the frequency of the problem and the constantly increasing use of cork in bottling no doubt explain the large number of extensive studies examining this issue. 

Crump, D. R., 1978, 2-Propylthietane, the major malodorous substance from the anal gland of the stoat. Tetrahedron Lett., 1978 5233. 

However, the malodorous substances of the beach marten Martes foina, of the pine marte Martes martes 318) of the raccoon Procyon lotor 324) and the subcaudal gland of the badger Meles meles are fatty acids rather than sulfur compounds 323). 

ACF can eliminate malodorous substance in the [57] air, especially for aryl substance which will generate carcinogens. 

In a few cases, even the raw oils directly isolated from the plant have been submitted to the transformation with syngas [67]. Product aldehydes possess an antimicrobial activity and have a pleasant smell. Therefore they can be used well with malodorous substances. In most cases, Rh or Co catalysts were submitted to hydroformylation. Also Pt/Sn catalysts should be taken into consideration, since undesired Wagner-Meerwein isomerization is suppressed. All aldehydes and acetals, as well as their mixtures, show woody, floral, and green, or balsam-like odors and can be employed as components of perfume accords. 

Some contaminants in a gas stream are neither chemical pollutants nor objectionable particulates. They are malodorous materials that are considered a nuisance if vented into the atmosphere. The maximum desired atmospheric level of a malodorous substance is defined as that concentration just below the threshold of detection by 50% of an odor panel. Table 5-7 gives this detection limit for many common malodorous substances [10]. Note that many substances can be sensed by the olfactory nerves at levels below one part per billion. For instance, hydrogen sulfide can be detected to one fifth of one ppb, while butyric acid (the principal odor from rancid butter) can be detected to one half of one ppb. 

Removal of organic odors is a much more complex problem. Wet scrubbing using a combination of absorbent and oxidant has successfully reduced such odors [11]. The malodorous substance first is absorbed into the liquid phase then the oxidant converts the absorbed contaminant to a less odorous substance. This sequence eliminates the normal Henry s Law vapor pressure that would be exhibited if the malodorous material simply were absorbed into water. 

D. R. Crump, The major malodorous substance from the anal gland... 

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