If the pH of wastewater flowing into a treatment facility is too low, which of the following can be added to adjust the pH to a neutral value?

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

Answer: (C)

When wastewater pH is too low, you raise pH by adding a base or buffering agent that neutralizes excess hydrogen ions. Sodium bicarbonate does this effectively: it dissolves to release bicarbonate ions, which react with the free H+ to form carbonic acid that quickly converts to carbon dioxide and water. This neutralizes acidity and adds buffering capacity, helping keep the pH stable around neutral. It’s a common, safer option for pH adjustment in treatment systems and also helps maintain alkalinity for downstream biological processes.

Gaseous chlorine and ferric chloride are not used to raise pH; chlorine gas can form acidic species in water and ferric chloride is itself acidic when dissolved, which would push pH lower. A carbonic polymer isn’t a standard pH adjuster and doesn’t reliably raise pH.