Groundwater will usually contain more of which?

Prepare for the American Water Works Water Treatment Plant Operator Test. Study with multiple choice questions, each with hints and explanations. Get ready to excel!

Groundwater picks up minerals from the rocks it flows through, so it often becomes high in hardness (calcium and magnesium ions) and alkalinity in the form of bicarbonate. When water interacts with carbonate rocks like limestone or dolomite, carbon dioxide in soil forms carbonic acid that dissolves minerals, releasing calcium, magnesium, and bicarbonate into the water. This combination—more hardness and more bicarbonate—is a common characteristic of groundwater. Oxygen tends to be lower underground because the water isn’t in contact with air and microbial processes consume available O2. Carbon dioxide and methane can appear in some groundwater under certain conditions, but they’re not the typical hallmark like hardness and bicarbonate. Color and taste vary with impurities and aren't a reliable indicator of groundwater composition.