How does alum hasten the process of sedimentation.

Explanation

**Step-by-Step Solution:**

1. **Understanding Sedimentation**: Sedimentation is the process where solid particles settle down from a liquid. This occurs when the particles are heavy enough to overcome the buoyant forces acting on them.

2. **Role of Alum**: Alum is a chemical compound that, when added to water, dissolves and interacts with impurities present in the water, such as clay and dust particles.

3. **Formation of Clusters**: When alum dissolves in water, it causes the smaller particles of impurities to clump together, forming larger aggregates or clusters. This process is known as coagulation.

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