CWEA Maintenance Technologist 2025 – 400 Free Practice Questions to Pass the Exam

The primary role of lime in wastewater treatment is pH adjustment and precipitation of heavy metals. Lime, which is primarily calcium oxide or calcium hydroxide, is added to wastewater to increase the pH level. This higher pH enhances the solubility of heavy metals, allowing them to form insoluble precipitates that can then be removed from the water. The precipitation process is critical because it helps in reducing toxic heavy metal concentrations, thereby protecting the environment and improving water quality.

The use of lime also aids in the overall stabilization of the wastewater, reducing the corrosiveness of the water. This dual action of adjusting pH and precipitating heavy metals makes lime an essential chemical used in various stages of wastewater treatment processes.