Which chemical is commonly used to adjust pH in water treatment when alkalinity is low?

Lime is commonly used to adjust pH in water treatment, particularly when alkalinity is low. Lime, or calcium hydroxide, increases the pH of water by providing hydroxide ions, which react with hydrogen ions to raise the pH level. Additionally, lime enhances the natural buffering capacity of the water, contributing to improved overall water quality.

Using lime is particularly beneficial in situations where the water has a low alkalinity because it helps stabilize the pH levels and reduces the potential for corrosivity in distribution systems. Other advantages include its ability to precipitate heavy metals and remove impurities, which is essential in achieving safe drinking water standards.

In contrast, soda ash, while also used for pH adjustment, is more effective when alkalinity is already present at lower levels than required. Chlorine is primarily utilized as a disinfectant and does not effectively change pH levels, nor does fluoride serve the purpose of pH adjustment in water treatment processes.