What is lime's effect on the solubility of toxic metals in wastewater treatment?

Lime is commonly used in wastewater treatment because of its ability to influence the chemistry of metals in solution. When lime is added to wastewater, it increases the pH of the water, which in turn affects the solubility of various metals. Many toxic metals, such as lead, cadmium, and copper, tend to form insoluble hydroxides at higher pH levels. As the pH rises due to lime addition, these metals precipitate out of the water as solid compounds, effectively reducing their solubility.

This process not only decreases the concentration of toxic metals in the wastewater, making it safer for discharge or further treatment, but it also facilitates the removal of these substances through sedimentation, filtration, or other separation methods. Therefore, the correct answer highlights lime's efficacy in decreasing the solubility of toxic metals in wastewater, contributing to more effective treatment processes.