Which of the following is a method to quantify turbidity levels in water?

The method to quantify turbidity levels in water is by using a turbidimeter. A turbidimeter is an instrument specifically designed to measure the cloudiness or haziness of a fluid, which is caused by large numbers of individual particles that are generally invisible to the naked eye. It operates by passing a light beam through a water sample and measuring how much light is scattered by the particles suspended in the water. This scattering is directly related to the concentration of particulate matter, thus providing a quantitative measure of turbidity.

In contrast, the other options listed serve different purposes: a colorimeter is used to measure the concentration of colored compounds in a liquid, a chlorinator is meant for adding chlorine to water for disinfection, and an alkalinity tester measures the buffering capacity of water rather than its turbidity. Understanding these distinctions helps clarify why the turbidimeter is the appropriate choice for gauging turbidity.