Many people associate clean and healthy water with water that has the best taste and smell. This is such a prevalent conception that many water treatment sites will compete in “best tasting water” competitions. However, taste and odor problems are rarely linked to health effects. Water treaters will treat taste and odor to improve customer satisfaction.
Water treaters conduct a threshold odor test and a flavor profile analysis to determine the various types of odors and smells that are present in the water supply. This analysis helps set the path forward to eliminate the foul taste and odor in drinking water.
Off tastes and smells in water originate from algae, bacteria, or pollution. Algae blooms are influenced by local environments from various forms of pollution: waste, both domestic and industrial, and run-off. Algae blooms can exist in relatively clean water, they are microscopic in size and do not normally constitute risks to health.These blooms present in raw water can then be a major contributor to foul taste and odor in treated water. Furthermore, various compounds derivative of industrial waste can impart foul odor and taste as well.
Industrial compounds such as phenols, hydrocarbons may exhibit foul odors as indicated by the threshold odor test at very low concentrations. Additionally, metals such as copper and zinc will yield a foul taste however not be present in the threshold odor test.
The flavor profile analysis will indicate specific tastes and odors that are present in the water supply. These flavors and odors are correlated to specific types of algae or pollution that lead to that result. Understanding the cause helps determine chemical dosing path forward.
Oxidation is one of the most effective methodologies to remove foul tastes and odors. Various types of oxidants, such as potassium permanganate, ozone, hydrogen peroxide, and chlorine dioxide are the most prevalent.
In other cases, chlorine or sodium hypochlorite are used to improve taste. As this chemical is also prevalently used for disinfection, a proper dose of the chemical is critical. To use chlorine for taste and odor control, a higher chlorine dose than what is used for disinfection is required. This process is known as superchlorination.
While this process can help remove grassy or fishy tastes and smells, it can make some odors worse. For example, superchlorination will negatively impact those odors linked to phenols. Once superchlorination takes place, the excess chlorine is typically removed through the use of carbon.
Accurate dosing pumps should be utilized to ensure the proper amount of chlorine is added to prevent residual taste and odor. Dosing accuracy minimizes chemical use and helps optimize the process.
Additionally, certain geographical areas may have hydrogen sulfide in the groundwater which in turn is found in well water. Hydrogen sulfide in the water supply creates a sulfur (“egg-like”) water smell. In these cases chemical feed pumps are used to add chemicals to the water system to eliminate the odor.