In wastewater treatment, why is hydroxide precipitation preferred over sulfide precipitation in some cases?

Hydroxide precipitation is often preferred in wastewater treatment due to the reduced health risks associated with handling and controlling hydroxides compared to sulfides. Sulfide precipitation can release toxic hydrogen sulfide gas, which poses significant health and safety hazards to workers and the environment. This gas can be harmful, causing respiratory issues and other health problems.

On the other hand, while hydroxide precipitation can effectively remove various metals from wastewater, it is generally more benign and safer for operators to manage. The byproducts of hydroxide treatment are typically less hazardous, contributing to a safer workplace. Additionally, since hydroxide does not produce toxic gases, the overall safety and health risks are minimized, making it a preferable choice in many situations where safety is a primary concern.