To raise the pH of acidic wastewater to neutral, which chemical is commonly added?

• A. Sodium Bicarbonate
• B. Gaseous Chlorine
• C. Ferric Chloride
• D. Carbonic Polymer

Answer: (A)

Raising the pH of acidic wastewater is about neutralizing excess hydrogen ions with a gentle base that also adds buffering capacity. Sodium bicarbonate fits this role well. When added, it dissociates into sodium ions and bicarbonate. The bicarbonate reacts with hydrogen ions to form carbonic acid, which quickly becomes carbon dioxide and water. This neutralizes the acidity and raises the pH, while also increasing the system’s alkalinity so future acid or base additions won’t swing pH as much.

This approach is preferred over the other options: a chlorine gas addition would not raise pH and can even introduce acids or reactive species; ferric chloride is acidic and used for coagulation, not pH control; and a nonstandard “carbonic polymer” isn’t a recognized pH adjuster. Sodium bicarbonate is a safe, common, and effective choice for mid-range pH adjustment in wastewater.