Which of the following is the main cause of taste and odor problems in treatment surface water?

• A. Bacteria in the distribution system
• B. Algae in the stream or impoundment above the intake
• C. Sediment deposition
• D. Alkalinity fluctuations

Answer: (B)

Algal blooms in the source water upstream of the intake are the primary cause of taste and odor problems in treatment surface water. When algae grow in the stream or impoundment, they release compounds such as geosmin and MIB that produce earthy or musty tastes and odors in the water. These compounds originate before treatment and can be tough to remove with standard coagulation and filtration, so the odor issues can carry through to the finished water unless odor-control steps like activated carbon are used. That’s why monitoring the source and applying appropriate treatment to address these odor-causing compounds is key. The other options can affect water quality in different ways, but they’re not the main source of taste and odor problems in surface water before treatment.