Which chemical is primarily used for pH adjustment in wastewater systems?

Lime is primarily used for pH adjustment in wastewater systems due to its effectiveness in neutralizing acidity and raising the pH level of the water. Lime, or calcium hydroxide, reacts with acidic components in the wastewater, which helps in stabilizing pH levels and reducing the corrosiveness of the water. This adjustment is crucial for both the efficiency of biological treatment processes and for meeting regulatory discharge standards.

Moreover, the use of lime has additional benefits beyond pH correction. It also contributes to the precipitation of certain heavy metals and can assist in the removal of phosphorus, providing a dual purpose in wastewater treatment. Its ability to improve the overall treatment process while being cost-effective makes it a common choice in many wastewater treatment facilities.

In contrast, other options might serve different functions in a wastewater treatment process but do not primarily focus on adjusting pH in the same effective manner as lime. For instance, sodium hydroxide is indeed used for pH adjustment but is less commonly employed compared to lime due to safety and handling considerations. Aluminum sulfate, while useful in coagulation, is not used primarily for pH adjustment. Hydrochloric acid would lower pH rather than raise it, making it unsuitable for the intended purpose of increasing pH levels in wastewater