Taste and odor removal

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. 

Function Decolorizing agent taste- and odor-removing agent purification agent in food processing. 

As such, it is used in water treatment to control taste and odors, remove color, and control biological growth. It promotes the removal of iron and manganese species by rendering them insoluble through oxidation ... 

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. 

Chemical oxidants that are commonly used to disinfect, control taste and odor, remove color, and/or provide microfiocculation, include free chlorine (HOCl/OCL), mono chloramine (MCA), chlorine dioxide (CIO2), permanganate (Mn04 ), and ozone (O3). Although the relative reactivity of these compounds varies greatly, very few studies have comprehensively examined their reactivity with transformation products. One comprehensive study showed that the relative reactivity of pesticides with these oxidants was, on average (Adams et al. 2007)... 

Pish protein concentrate and soy protein concentrate have been used to prepare a low phenylalanine, high tyrosine peptide for use with phenylketonuria patients (150). The process includes pepsin hydrolysis at pH 1.5 ptonase hydrolysis at pH 6.5 to Hberate aromatic amino acids gel filtration on Sephadex G-15 to remove aromatic amino acids incubation with papain and ethyl esters of L-tyrosine and L-tryptophan, ie, plastein synthesis and ultrafiltration (qv). The plastein has a bland taste and odor and does not contain free amino acids. Yields of 69.3 and 60.9% from PPG and soy protein concentrate, respectively, have been attained. 

Potable water treatment Granular activated carbons (GAC) installed in rapid gravity filters Removal of dissolved organic contaminants, control of taste and odor problems... 

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. 

At present, chlorine dioxide is primarily used as a bleaching chemical in the pulp and paper industry. It is also used in large amounts by the textile industry, as well as for the aching of flour, fats, oils, and waxes. In treating drinking water, chlorine dioxide is used in this country for taste and odor control, decolorization, disinfection, provision of residual disinfectant in water distribution systems, and oxidation of iron, manganese, and organics. The principal use of chlorine dioxide in the United States is for the removal of taste and odor caused by phenolic compounds in raw water supplies. 

Lalezary, S., Pirbazari, M., and McGuire, M.J. Evaluating activated carbons for removing low concentrations of taste and odor producing organics, / Am. Water Works Assoc., 78(ll) 76-82, 1986. 

Chiang, P.C. Etzel, J.E. Procedure for selecting the optimum removal process for cationic surfactants. In Toxic and Hazardous Waste-, LaGrega, Hendrian, Eds. Butterworth Boston, MA, 1983. Cohen, J.M. Taste and Odor of ABS-, US Dept, of Health, Education and Welfare Dept. Cinciimati, OH, 1962. 

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. 

If properly used, AOPs generally result in higher oxidation rates than ozone alone, but need to be evaluated for effectiveness, costs and possible side effects (Glaze, 1987). However, for removing taste and odor problems in drinking water, ozone alone is sufficient without the addition of hydrogen peroxide or ultra violet radiation. 

---