What is a consequence of excess lime in water treatment?

Excess lime in water treatment primarily acts as a softening agent. When lime (calcium hydroxide) is added to water, it reacts with bicarbonate hardness (calcium and magnesium bicarbonates), converting them into insoluble precipitates, mainly calcium carbonate. This process decreases the overall hardness of the water by removing these hardness-causing minerals. Therefore, the presence of excess lime is beneficial in reducing water hardness, which can lead to improved water quality and reduced scaling in pipes and appliances.

The other options may appear relevant in some contexts but do not accurately reflect the primary consequence of excess lime in water treatment. For example, while excess lime may indirectly impact magnesium levels, it does not specifically increase them, nor does it prevent scaling effectively if present in excess. Additionally, lime does not significantly enhance the taste of water; in fact, it can impart an undesirable flavor if not managed correctly. Understanding the mechanism of how lime functions within the treatment process highlights why the reduction of hardness is the key consequence here.