Which combination is used to coat sedimentation basin walls to rid the basin of slime growth?

• A. copper sulfate and lime
• B. sodium carbonate peroxyhydrate
• C. dimethylalkylamine and lime
• D. zinc pentahydrate

Answer: (A)

Controlling slime on sedimentation basin walls relies on forming a protective biocidal coating that makes the surface inhospitable to algae and slime-forming organisms. Copper sulfate provides copper ions that are toxic to algae and many bacteria, reducing growth on contact with the coated surface. Lime helps establish and maintain a durable film on the walls by adjusting pH and promoting deposition of calcium carbonate, which helps the coating adhere and stay effective. Together, they create a lasting coating that keeps slime from re-establishing on the basin walls between cleanouts.

Other options don’t provide this combination of a lasting coating plus active biocide. Sodium carbonate peroxyhydrate is an oxidant and wouldn’t form the stable wall film needed for long-term slime control. Dimethylalkylamine with lime isn’t a standard, proven wall-coating regimen for basins. Zinc pentahydrate acts as a biocide but isn’t used with lime to create the same durable coating on basin walls.