Principles and Practice of Engineering (PE) Civil: Water Resources and Environmental (WRE) Practice Exam

Lime is specifically used to increase the pH of water due to its basic properties. It is a substance that contains calcium hydroxide (often referred to as hydrated lime) or calcium carbonate. When lime is added to water, it reacts to produce hydroxide ions, which increases the alkalinity and thereby raises the pH level of the water. This process is commonly employed in water treatment facilities to reduce acidity and improve water quality for various applications, including drinking water.

In contrast, substances like carbon dioxide and sulfuric acid are acidic and will lower the pH of water when added. Carbon dioxide, when dissolved in water, forms carbonic acid, which contributes to lower pH levels. Sulfuric acid is a strong acid that directly decreases pH upon dissolution. Chlorine is primarily used for disinfection purposes and does not significantly affect pH levels in the way that lime does. Therefore, lime stands out as the substance that effectively increases water pH.