Which chemical is commonly used to raise pH levels in water?

Lime, specifically calcium hydroxide, is commonly used to raise pH levels in water due to its effectiveness in neutralizing acidity. When lime is added to water, it dissociates to release hydroxide ions, which increases the pH by making the water less acidic. This process is crucial in water treatment to improve water quality, enhance the effectiveness of disinfection processes, and prevent corrosion in distribution systems.

Other chemicals may serve different purposes, such as chlorine, which is primarily used for disinfection rather than pH adjustment, and ammonia, which can affect pH but is not a straightforward pH raiser. Baking soda, or sodium bicarbonate, can have a mild effect on pH but is less commonly used for significant pH adjustments in water treatment compared to lime. Thus, lime is the preferred choice for effectively and consistently raising the pH in water systems.