Taste and odor is one component of drinking water’s aesthetic quality. The Water Authority in recent years has been experiencing some of the worst episodes of summer taste and odor in its 90-year history. Although water sometimes has a taste and odor, it is 100% safe to drink.
Decaying vegetation and byproducts of microbia are probably the most universal sources of taste and odor problems in surface water. The organisms most often linked to taste and odor problems are the filamentous bacteria actinomycetes and the blue-green algae.
Two highly studied by-products of actinomycetes and the blue-green algae are geosmin and methylisborneol (MIB). These compounds are responsible for the common earthy-musty odors in water supplies and have been isolated from many genera of actinomycetes and the blue-green algae. Both geosmin and MIB can have odor threshold concentrations of less than 10 parts per trillion.