How are pollutants cleaned or removed from the environment?

Certain substances, such as salt that is left behind when water evaporates from a body of water—which happens in oceans and seas—do not evaporate readily even when they are thoroughly mixed with water.

Running waters are easily oxygenated; pollutants that are treated by oxygen degrade in a stream or river from upstream to downstream, removing biodegradable organics in the process.

There are four principal photochemical reactions of environmental significance: direct photolysis, indirect photolysis, oxidation, and free-radical oxidation. Chlorinated compounds are particularly susceptible to oxidation. Photochemical transformations are important fate processes for organic constituents in the near-surface aquatic environment and in the upper atmosphere. Enhanced photochemical processes are also being used for the treatment of some hazardous wastes.

Pollutants are removed from the environment through processes such as filtration, sedimentation, chemical treatment, and bioremediation. Additionally, technological methods like air and water purification systems are employed to reduce pollution.