In streams it is influenced by rocks and soils, salts, certain plant activities, and certain industrial wastewater discharges. Alkalinity is significant in many uses and treatments of natural waters and wastewater. It is important for fish and aquatic life because it protects or buffers against rapid pH changes. Higher alkalinity levels in surface waters will buffer acid rain and other acid wastes, and prevent pH changes that are harmful to aquatic life. Alkalinity can be defined several ways.
Alkalinity is the ability to neutralize acids.
It is the amount of strong base that needs to be neutralized to bring a solution to a pH equivalent to that of a pure CO 2 system. It is also a measure of how much acid the impurities in water can absorb when the pH drops below a certain level. Because the alkalinity of many surface waters is primarily a function of carbonate, bicarbonate and hydroxide content, it is usually taken as an indication of the sums of concentration of these constituents. Bicarbonates represent the major form of alkalinity, since they are formed in considerable amounts from the action of carbon dioxide upon basic materials in the soil. If CaCO 3 actually accounts for most of the alkalinity, hardness in CaCO 3 is equal to alkalinity.