In other words, alkalinity represents the ability of water to neutralize acids when there are changes in pH in a water sample. The alkalinity of water is determined by the concentration of conjugate bases of inorganic carbon and organic acids as well as orthophosphates, ammonia and silicate, which have the ability to consume acid when added to water.

In general, the conjugate bases found in water supplies and water treatment applications are usually derived from inorganic carbon. Generally, alkalinity is expressed in milligrams per liter of calcium carbonate (mg/L CaCO3).

When talking about alkalinity, we can sometimes also refer to the buffering capacity of water. Although these two concepts are not the same, they are closely related. To reiterate, alkalinity is a measure of water's ability to neutralize acids. The buffering capacity of water, on the other hand, is the ability of water to resist pH fluctuations that may be caused by changes in water quality. Although they are closely related, alkalinity and buffering capacity differ since an alkaline concentration may have different buffering capacities depending on the type of contaminants in the sample. This is because some alkaline compounds have a higher neutralizing capacity than others.

Finally, to measure the alkaline property of a water sample, one commonly used method is to add acid to the sample. Specifically, the initial pH must be calculated and as the acid is added, the acidity of the sample must be measured. Initially, the acid that is added will be neutralized by alkaline compounds such as bicarbonate, but as the acid is added, these alkaline compounds become depleted, and the acid takes over. From this point on, the addition of acid will cause the pH to drop linearly. The point at which the pH changes become linear, thus the point at which the alkaline compounds are depleted, is used to determine the alkalinity. The titration method must now be used to determine the alkalinity of the sample.