What is the purpose of a day tank in a water treatment system?

A day tank plays a crucial role in water treatment systems by providing a dedicated space for the premixing of chemicals before they are introduced into the water supply. This premixing is essential for ensuring that the chemicals are properly diluted and homogeneous, allowing for more effective treatment of the water. By using a day tank, operators can also control the dosage of chemicals being fed into the system, monitor the concentration of the solutions, and make necessary adjustments based on real-time water quality data.

In contrast, the other options do not accurately reflect the function of a day tank within the context of water treatment. The second option about the storage of non-water treatment chemicals suggests a different purpose that does not align with the operational use of a day tank. The third option regarding testing water stabilizers in a laboratory pertains to a completely different setting focused on analysis rather than the immediate preparation of treatment solutions. Therefore, the primary function of a day tank is indeed to facilitate the premixing of treatment chemicals before they are added to the treated water.