Wastewater Grade 5 Practice Test

The process of "slaking" specifically refers to the reaction that occurs when quicklime, which is calcium oxide, is mixed with water. This reaction involves the hydration of calcium oxide to form calcium hydroxide, often referred to as slaked lime. This process is crucial in various wastewater treatment operations because it helps raise the pH of the water, facilitating the removal of impurities and improving the overall treatment process.

In contrast, the other options describe different processes or substances unrelated to the hydration process typically associated with slaking. For example, heating calcium hydroxide does not reflect the action of slaking, as slaking specifically pertains to adding water to quicklime. Cooling down sludge or mixing with activated sludge also does not accurately represent the slaking process. Therefore, the answer emphasizes the essential nature of the hydration of calcium oxide in effective wastewater management practices.