Water Well Journal
Issue link: http://read.dmtmag.com/i/498253
Taste and Odor Mechanism in the Human Body Sensations of taste and odor are the result of chemical stimulation of the ap- propriate human nerve cells. Because of this reaction, taste and odor are known as "chemical senses." Taste and odor affect the quality of water in various ways—reducing its aesthetic and desir- ability qualities, affecting the enjoyment of certain foods and beverages, and completely destroying the palatability of drinking water in some cases. Taste and odor differ in both the na- ture and location of the receptor nerve sites. Nerve sensors for odors are found high in the nasal cavity, while the nerve sites for taste are distributed over the entire tongue. In the case of water, odor sensations are stimulated by vapors and do not require physical contact, whereas physical contact is required with the taste buds within the mouth for taste sensations. Tasting is a complex sensation result- ing in a combination of taste, odor, tem- perature, and physical feel—also known as flavor. Laboratory tests exist to deter- mine the level of taste or odor in a water sample as well as to determine the palatability. For odors, the test is referred to as a threshold odor number (TON), meas- ured by a scale beginning with 0 (no odor) up to levels of more than 10,000 with a TON of 3 the recommended limit. In the case of taste, even though a taste threshold test exists, the major concern is to determine the acceptability of drinking water from a judgment call based on sensory evaluations. This judg- ment is made through use of a taste- rating test in which a panel of water consumers taste and rate various sam- ples of water, usually obtained through separate treatment processes. Although taste and odor problems are seldom connected to toxicological effects, they are nevertheless important considerations as they may be the first alarm signal for a potential health hazard and play an obvious role in the aesthetic quality of the water. They also play an important role in the consumer's evalua- tion of their own drinking water supply, to the point of even affecting the amount of water they consume and purchase. Treatment Techniques for Control of Taste and Odor Problems Most taste and odor problems are dealt with by eliminating the substance causing the problem. Usually, once the offending substance is identified, the proper treatment system can be selected. Treatment techniques for taste and odor control can be usually divided into three major categories: (1) filtration, (2) demineralization, and (3) disinfection/ oxidation. Often, a combination of two or more of these processes may be necessary to completely eliminate a specific taste and odor problem. Filtration Filtration, specifically filtration using activated carbon media and also known as granular activated carbon (GAC), is generally the most successful method of eliminating taste and odor problems. Although the process resembles filtra- tion, the more appropriate term of "contactor" is preferred when consider- ing the use of GAC. ENGINEERING continues on page 56 Twitter @WaterWellJournl WWJ May 2015 55 c ear S , ts a r er all t m alar olume c air v ippers air str gers air char s t y tion equipmen a aer ope , r ers adapt A em o r igs to om r r F c Se c ar ear ear Sear S o f ching f c c n c ir th mill t oduct media r tion at om om om clam chlo chem chem chec o ching f ching ching f hi f g f g ching f or some or some or so or or some or some me r some or so ething? ething? g? ething? ething ething? ething? casin casin casin i tion wheels ic , fr ool , cable t bits ds , cable guar bits on , butt bits inders r bit g ool essers and t bit dr e pe a onit t ben ings bear in bank bailers B a aug aug AS ar ers Buy ir A D NGW or ser ou , find t e y vic d t ig es vic ser g om r r F dec da D c cr c c or c or c on on c on c n c c eel ed st t ica , fabr ngs , spiders & slips ools ng t wnhole do - er ng cutt ers h) le or t . uide s G y & need in the or t ect r & the pr t oduct the p eed o deae ta ylin an ou ou e e v t t t ond om om u u n Guid e Buy Onlin de rs ne w w t en c th ca casin casin casin casin casin casin casin casin tal on iz , hor bits ill , dr bits ag , dr bits -hole wn-the , do bits , diamond bits bide , car bits ems , st ool , cable t bits , sockets ool , cable t bits , jars ool , cable t bits tion wheels ic , fr ool , cable t bits . N G W w w dir der dec ers aliz r eads eaded PVC , thr ngs eflon , T ngs eel , stainless st ngs , shoe ngs , PVC ngs , plastic ngs glass , fiber ngs eel ed st t ica , fabr ngs A e dies desi desa desa r dep deio equ o u Guid de