• Filtration is a physical method that can only separate the pathogens and other contaminants from water but cannot kill microorganism.
• Boiling kills all the pathogens at boiling temperature.
• Chlorine kills pathogens such as bacteria and viruses by breaking the chemical bonds in their molecules.
• Distillation relies on evaporation to purify water. Contaminated water is heated to form steam. The boiling process kills microorganisms such as bacteria and some viruses.

Source: ForumIAS