What happens to heavy metals when lime is added to wastewater?

When lime is added to wastewater, it typically reacts with heavy metals to form metal hydroxides, which are not soluble in water. This process leads to the precipitation of heavy metals out of solution, effectively removing them from the wastewater. By elevating the pH of the water, lime promotes the formation of these insoluble compounds that can then be separated from the liquid, typically through sedimentation or filtration. This method is a common practice in wastewater treatment to reduce the concentration of heavy metals before the effluent is discharged or further treated. The other potential options, like increased solubility, evaporation, or conversion to gas, do not accurately reflect the chemical interactions occurring when lime is introduced to wastewater.