what are the objects used in a WATER PURIFICATION?please answer fast

Water can be purified in different ways. In chlorination, chlorine is the main object to remove undesirable substaces. In filtration, the major materials are soil, gravel, potting soil, cotton balls, scrap material, charcoal, sand, woodchips, Styrofoam packing, charcoal briquettes, etc. Likewise, different materials are used in different methods.