What effect does the addition of chlorine gas have on the pH of wastewater?

The addition of chlorine gas to wastewater primarily results in a decrease in pH. This occurs because chlorine gas (Cl2) reacts with water to form hydrochloric acid (HCl) and hypochlorous acid (HOCl). The formation of these acids contributes hydrogen ions (H+) to the solution, which lowers the pH.

In wastewater treatment processes, maintaining the correct pH is critical not only for ensuring the efficacy of the disinfection process but also for protecting downstream biological treatment systems. Typically, a lower pH can impact the solubility and reactivity of various elements and compounds present in wastewater, as well as affect the efficiency of chlorine as a disinfectant.

Understanding this behavior is essential for operators to manage and adjust chemical dosages appropriately in treatment processes.