Filtration is a mechanical process that separates solids from liquids or gases by passing the fluid through a medium that allows only the fluid to pass. Filtration is used in processes like water treatment and sewage treatment to remove undesirable constituents. Distillation is a process that separates mixtures based on differences in volatility, where the mixture is boiled and the vapor is condensed to separate components. Distillation has commercial uses like separating crude oil fractions and purifying water and air.