Taste and odour control in water supplies

TASTE AND ODOUR CONTROL

Most customers judge the quality of drinking water by taste and odor. If the customer is satisfied with these qualities, it is assumed the water is safe to drink. Oxidation, aeration and adsorption can be effective in reducing taste and odor.

Odour
One of the most common methods for measuring odor in water is the threshold odor test. It involves a series of flasks presented to an observer, who is told that some of the samples contain odors and that the series is arranged in order of increasing concentrations. The observer is also given a known odor-free blank for reference during the test..

• Methane gas from the decomposition of organic matter tastes like garlic and the biggest danger from the presence of methane is its explosiveness. 
• It can be removed by aeration.
• Hydrogen sulfide (H2S) in water is a common problem
• The most common method of removing hydrogen sulfide from water is by aeration. Carbon adsorption is also effective, but more expensive.
• Oxidation is the best method for controlling taste and odor problems.Oxidation can be carried out with the following chemicals: 
• Potassium permanganate, (most often used and is a very strong oxidant; dosage range of 0.1 to 0.5 mg/l can control taste and odor problems.)
• Ozone is also effective oxidizing of taste and odor compounds. Ozone changes the characteristics of the taste and odor by using Ozone dosages of 2 mg/l to 5 mg/1 
• A combination of ozone and hydrogen peroxide is superior to the use of ozone alone
• Chlorine dioxide or chorine are also effective methods of taste and odor control

Aeration is a practical solution for taste and odor control when the problem is caused by volatile compounds, such as hydrogen sulfide

Adsorption 

Adding powdered activated carbon to water or using of granular activated carbon (GAC) in the water filter can remove taste and odor.

Powdered activated carbon (PAC) is the preferred method when the taste and odor is moderate and infrequent

Granular activated carbon filters should be considered when moderate-to-severe taste and odor problems exist frequently

Taste and odors occurring in the distribution system are primarily the result of corrosion of pipe material and/or growth of iron bacteria, such as crenothrix and leptorix, in the water main.