What is a hydrometer used for in water treatment?

A hydrometer is an instrument designed to measure the specific gravity of liquids, which in the context of water treatment, is often used to assess the concentration of solutions, such as acid concentrates. By determining specific gravity, operators can evaluate the density of the liquid, which is crucial in applications such as chemical dosing, where understanding the concentration of an acid or other additives helps ensure correct and safe mixing ratios.

In water treatment processes, knowing the specific gravity of acid concentrates can assist in monitoring the effectiveness of the treatment being applied and can also help in ensuring that the concentrations remain within safe and effective limits for the system operation. This capability is foundational for maintaining optimal water quality and preventing system damage or inefficiencies.

The other options, while related to water treatment, do not accurately describe the function of a hydrometer. Measuring water pressure, indicating pH levels, or determining water temperature requires different tools and methodologies, making them unsuitable functions for a hydrometer.