The image below shows an activity performed by Varsha using muddy water. Based on the observation, answer the following questions.
Varsha notices that muddy water from a pond does not become clear even after standing for a long time. Her teacher suggests adding a small amount of alum (fitkari) and stirring it gently. After some time, she observes that the dirt particles clump together and settle at the bottom, leaving clear water on top.
1. Which method of separation is used in this process?
2. Which substance acts as a coagulant in the given case study?
3. Why is coagulation necessary before filtration in muddy water?