Odors, removal carbon

H2S or CH the latter always contains associated impurities that have taste and odor. Removal of these gases can be accompHshed by adsorption (qv) with activated carbon (qv) oxidation with chlorine, potassium permanganate, or o2one or aeration. 

Other industries of interest are (1) the manufacturing of spices and flavorings, which may use activated carbon filters to remove odors from their exhaust stream (2) the tanning industry, which uses afterburners or activated carbon for odor removal and wet scrubbers for dust removal and (3) glue and rendering plants, which utilize sodium hypochlorite scrubbers or afterburners to control odorous emissions. 

Hansen R.E. Granular Carbon Filters for Taste and Odor Removal. JAWWA 1972, 64, No 3, pp.l76-181. 

The water purification properties of carbon adsorbents have been recognized for more than two millennia, wood chars having been utilized for tins purpose, as early as 200 B.C. [ 1 ]. Modern applications of adsorbents in water supply practice have their roots in the development of public treatment systems in the early 10th century. By the mid 1800 s charcoal was used for taste and odor removal in a number of municipal water plants in England [ 2 ], and more than twenty large scale carbon filtration plants were built and put into operation in the U.S. before the turn of that century [3 ]. 

Alternatives most frequently considered for taste and odor removal include breakpoint chlorination, aeration, ozonation, and oxidation with chlorine dioxide or potassium permanganate. None of these technologies have been found to approach the activated carbon adsorption process iri terms of effective treatment for this particular water quality problem. Another alternative is sorption onto other solids such as bleaching clays, synthetic resins or manganese dioxide. A brief summary of the advantages, disadvantages and cost factors associated with adsorption and alternative treatments for removal of tastes and odors... 

Figure 1 summarizes the most common modes of carbon use in water treatment. While replecement of sand by GAC in conventional filter plants may be satisfactory for taste and odor removal and general organic reduction, there is some concern that the contact time (approximately 8—10 minutes) associated with traditional 304nch deep filter beds may be insufficient for obtaining acceptable removal of to.xic and otherwise potentially hazardous organic substances [12—14 ], and that post-filter contactor columns may therefore be required in some applications. 

Treated and filtered wastewater can be recycled for use in irrigation. An important issue is odor removal prior to reuse. For a wastewater that has an initial concentration of 10 ppm of these compounds, the following test results are obtained when activated carbon is used to adsorb them ... 

Adsorbit [Bamebey Sutcliffe] Activated carbon odor remover. 

The contribution of activated carbon to improved quality of product is not always fully recognized characteristics such as freedom from haze, absence of foam, and other less visible benefits are often overlooked. It is worth noting that many of these less evident benefits are often a by-product incidental to the use of carbon for color and odor removal—and hence can often be obtained for little if any extra cost. For the most part, all that is ordinarily required is a selection of appropriate operating conditions. 

The phenol test also gives a good index of the relative odor-removal power of carbons, but the test is less convenient to conduct. 

Caustic activated carbons as hydrogen sulfide odor removal media... 

Varies Odor removal from waste gases (active carbon)... 

Applications. The applications of activated carbons form a large and growing market and are found in color and odor removal, in water purification, toxic-gas removal, general air purification, metal-ion adsorption for metal recovery, decoloration and purification of sugar, pharmacology, and chromatography. 

Although it is not effective in removing potentially toxic contaminants, general ventilation is often acceptable in providing comfort ventilation to control humidity, ternperamre, odors and carbon dioxide build-up and to remove dusts and biological agents from the air supply. 

Principal requirements of carbon for use in odor-removal equipment are a high capacity and low pressure drop. The material must also be dustless.. Specifications for activated carbon used in air purification are presented in Table 12-33. Typical commercial equipment is illustrated in Figure 12-51,12-52, and 12-53. 

Example 15.4-1 Odor removal We have been removing odor from a Miimesota resort s water supply using a bed of activated carbon. The bed s breakthrough is in 38 days, and its exhaustion is in 46 days. Because of seasonal demand, we want to double the water flow through the bed. We suspect that the mass transfer coefficient will be constant. If it is, when will breakthrough occur now ... 

The extent of purification depends on the use requirements. Generally, either intense aqueous extractive distillation, or post-treatment by fixed-bed absorption (qv) using activated carbon, molecular sieves (qv), and certain metals on carriers, is employed to improve odor and to remove minor impurities. Essence grade is produced by final distillation in nonferrous, eg, copper, equipment (66). 

Physica.1 Properties. Carbonyl sulfide [463-58-1] (carbon oxysulfide), COS, is a colorless gas that is odorless when pure however, it has been described as having a foul odor. Physical constants and thermodynamic properties are Hsted ia Table 1 (17,18). The vapor pressure has been fitted to an equation, and a detailed study has been made of the phase equiUbria of the carbonyl sulfide—propane system, which is important ia the purification of propane fuel (19,20). Carbonyl sulfide can be adsorbed on molecular sieves (qv) as a means for removal from propane (21). This approach has been compared to the use of various solvents and reagents (22). 

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