What method is used to control sulfide reagent addition when treating common metal wastes by sulfide precipitation?

The method that involves measuring residual sulfide concentration is crucial in controlling sulfide reagent addition during the treatment of common metal wastes through sulfide precipitation. This method ensures that the right amount of sulfide is added to precipitate the heavy metals effectively without exceeding the necessary levels.

By measuring the residual sulfide concentration, operators can determine whether there is still an adequate amount of sulfide present to react with the metals in the solution. This allows for precise adjustments to the amount of sulfide reagent being added, optimizing the treatment process and minimizing the risk of undesired side reactions or excessive sulfide levels, which might lead to other complications, such as the formation of odors or toxic conditions.

Therefore, monitoring the residual sulfide concentration is a reliable and effective means of managing the chemical processes involved in metal wastewater treatment, ensuring both efficacy and safety.