Odor in Water

There are many different types of bad tastes and odors in water. Troublesome compounds, chemical, and mineral may result from biological growth or industrial activities. These tastes and odors may be produced in the water supply, in the water treatment plant from reactions with treatment chemicals, in the distribution system, and/or in the plumbing of consumers. Tastes and odors can be caused by mineral contaminants in the water, such as the "salty" taste of water when chlorides are 500 mg/l or above, or the rotten egg smell in water caused by hydrogen sulfide. Odor in the drinking water is usually caused by blue-green algae. Moderate concentrations of algae in the water can cause it to have a "grassy", "musty" or "spicy" odor. Large quantities can cause the water to have a "rotten", "septic", "fishy" or "medicinal" odor. Decaying vegetation is probably the most common cause for taste and odor in surface water supplies. Hydrogen sulfide gas also occurs naturally in some groundwater, and both of these reasons help to crate that unpleasant sulfur smell in water. Furthermore, in treated water supplies chlorine can react with organics and cause odor problems. Odor is listed in the Secondary Drinking Water Standards by the US EPA. The contaminant effects are strictly aesthetic and a suggested Threshold Odor Number (TON) of 3 is recommended.  
 
Treatment and how to remove odor from water - Odor can be removed from water by oxidation-reduction or by activated carbon adsorption. Aeration can be utilized if the contaminant is in the form of a gas, such as H2S (hydrogen sulfide). Chlorine is the most common oxidant used in water treatment, but is only partially effective on taste and odor. Potassium permanganate and oxygen are also only partially effective. Chloramines are not at all effective for the treatment of taste and odor. The most effective oxidizers for treating taste and odor are chlorine dioxide and ozone. Activated carbon block water filters have an excellent history of success in treating taste and odor problems. The life of the carbon depends on the presence of organics competing for sites and the concentration of the odor causing compound.