What effect does hydrated lime have on the alkalinity of wastewater?

Hydrated lime, when added to wastewater, has a significant impact on its alkalinity by increasing the pH level. Alkalinity is a measure of the water's ability to neutralize acids, and it is often expressed in terms of the presence of bicarbonate, carbonate, and hydroxide ions. Hydrated lime, or calcium hydroxide (Ca(OH)₂), dissociates in water to release hydroxide ions, which increases the concentration of these alkaline substances in the water.

When hydrated lime is introduced to wastewater, it reacts with acids present in the water, effectively neutralizing them. This process leads to an increase in the hydroxide ion concentration, resulting in a higher pH, which is indicative of increased alkalinity. Furthermore, as the alkalinity rises, it aids in the treatment process, such as promoting the precipitation of heavy metals and enzymes for biological treatments.

This adjustment of pH and its effect on alkalinity makes hydrated lime a crucial additive in wastewater treatment, particularly for processes requiring effective acid neutralization.