If algae or slime growth in sedimentation basins are a problem, drain the basin and apply a solution of ______ per liter of water using a brush to remove the growth.

• A. 5 g of Copper Sulfate and 5 g Lime
• B. 10 g of Copper Sulfate and 10 g Soda Ash
• C. 10 g of Copper Sulfate and 10 g Lime
• D. 5 g of Copper Sulfate and 10 g Soda Ash

Answer: (C)

Copper sulfate acts as an algaecide to kill algae in the basin, while lime provides buffering to raise and stabilize the pH, which helps copper stay effective and makes brushing off the growth easier during cleaning. Dosing 10 grams of copper sulfate with 10 grams of lime per liter of water gives enough copper to kill the algae and enough lime to maintain a pH level that supports the treatment and subsequent removal. Underdosing the copper would leave the algae, and substituting soda ash for lime changes the buffering chemistry and can reduce effectiveness or create other handling issues. The balanced combination of copper sulfate and lime is the most reliable approach for clearing algae and slime in sedimentation basins.