What is the main cause of object taste and odor in water?

The primary cause of objectionable taste and odor in water is often associated with algae. Algae can produce various metabolites, such as geosmin and 2-methylisoborneol, which are responsible for earthy and musty tastes and smells. When conditions are favorable, such as warm water temperatures and nutrient-rich environments, algae can proliferate, leading to noticeable changes in the sensory characteristics of the water.

While minerals, nitrogen, and oxygen can influence water quality and might contribute to other issues, they are not the main contributors to the specific problem of taste and odor. Minerals may cause hardness or settle as precipitates, nitrogen can lead to algal blooms under certain conditions but does not directly create taste and odor, and oxygen is crucial for aquatic ecosystems but does not impart flavor or smell. Therefore, the presence of algae and the compounds they release is the most direct cause of undesirable tastes and odors in water.