What does pH measure in water?

pH measures the hydrogen ion concentration in water, which reflects the acidity or alkalinity of the water. The pH scale ranges from 0 to 14, where a pH of 7 is considered neutral, values below 7 indicate acidic conditions (higher hydrogen ion concentration), and values above 7 indicate basic or alkaline conditions (lower hydrogen ion concentration). Understanding pH is essential in water treatment as it affects various chemical processes, biological activity, and the overall quality of the water.

The other options relate to different parameters: oxygen levels refer to dissolved oxygen, which is crucial for aquatic life; temperature measures the warmth or coolness of water and affects solubility and biological processes; clarity of water is related to turbidity and particulate matter but does not directly relate to pH.