Which treatment method is associated with lowering alkalinity in water?

The treatment method associated with lowering alkalinity in water is the use of hydrochloric acid feed. Alkalinity is a measure of the water's capacity to neutralize acids, primarily due to the presence of bicarbonates, carbonates, and hydroxides. By introducing hydrochloric acid into the water, the pH is lowered, and the bicarbonate and carbonate ions are converted into dissolved carbon dioxide and water. This reaction effectively reduces the alkalinity, as the alkaline compounds that contribute to the buffering capacity of the water are neutralized.

In contrast, other methods such as ion exchange, filtration, and centrifugation generally do not specifically target alkalinity reduction. Ion exchange can remove specific cations or anions but does not inherently lower alkalinity unless specific acidic conditions are created. Filtration primarily focuses on the physical removal of particles and does not alter the chemical composition regarding alkalinity. Centrifugation separates substances based on density but does not chemically interact with the water to affect its alkalinity. Thus, the only method that specifically facilitates the reduction of alkalinity in water is the hydrochloric acid feed.