Alum, also known as aluminum sulfate, is sometimes used as a water treatment agent to clarify water by removing suspended particles and impurities. When using alum for water purification, the duration of contact between alum and water depends on the specific application and the water quality you are trying to treat.
In general, the process of water purification using alum involves the following steps:
Prepare a stock solution: Dissolve alum in water to create a concentrated solution. The recommended concentration can vary depending on the specific water treatment requirements and guidelines provided by local authorities or water treatment professionals.
Coagulation: Add the alum solution to the water you want to purify and stir gently to ensure proper mixing. The alum reacts with the impurities and suspended particles in the water, forming larger flocs that can settle or be easily removed.
Settling: Allow the treated water to sit undisturbed for a period of time to allow the flocs to settle to the bottom of the container. The duration of settling can vary depending on factors such as water temperature, the concentration of alum used, and the nature of the impurities present in the water.
Decantation or filtration: After the settling period, carefully pour or siphon off the clarified water from the top, leaving the sediment at the bottom of the container. Alternatively, you can pass the settled water through a filter to remove any remaining particles.
The specific time required for settling will depend on the water quality and the effectiveness of the alum treatment. It can range from a few hours to overnight. It's important to note that alum treatment may not effectively remove all types of contaminants, such as dissolved substances or microorganisms, so it's advisable to consult local water treatment guidelines or consult with a water treatment professional for specific recommendations based on your situation.