Which process involves the use of microorganisms to break down organic materials?

The process that involves the use of microorganisms to break down organic materials is called biological treatment. This method relies on bacteria and other microorganisms to decompose organic waste found in wastewater. During biological treatment, these microorganisms consume the organic compounds, thus reducing the overall organic load and improving the quality of the wastewater.

Biological treatment can occur in several forms, including activated sludge systems, trickling filters, and lagoons, all designed to promote the growth of microorganisms that effectively digest organic materials. This process is essential in the wastewater treatment cycle, as it significantly reduces pollutants, making the water safer for discharge into the environment or for further purification.

Filtration, chlorination, and precipitation are all treatment processes, but they do not primarily rely on microorganisms to break down organic matter. Filtration is a physical separation process that removes particles, chlorination is a disinfection method that uses chlorine to kill pathogens, and precipitation involves chemical reactions to separate solids from liquids. Therefore, biological treatment stands out as the most relevant process involving microorganisms for the breakdown of organic materials.