Excessive algae growth in a presedimentation impoundment is best controlled by:

• A. Line the bottom to limit nutrients for the algae to grow
• B. Cover the impoundment
• C. Chlorinate to kill the algae
• D. Use potassium permanganate to reduce the number of algae

Answer: (B)

Blocking light stops photosynthesis, the process algae need to grow. In a presedimentation impoundment, covering the water surface prevents sunlight from reaching algae, which directly reduces or prevents blooms and the downstream issues they cause in treatment. This preventive approach targets the root cause—light availability—without the downsides of chemical treatments or costly structural changes.

Lining the bottom to limit nutrients isn’t a reliable, practical solution for surface algae, since nutrients can still be present in the water column and sunlight at the surface drives growth. Chlorination would kill algae but is a chemical treatment that adds disinfectant demand and byproducts and doesn’t prevent growth. Potassium permanganate can oxidize some compounds but isn’t a dependable method for controlling algal blooms and also introduces chemical handling concerns.