Why is municipal sewage first separated into degradable and non degradable waste?

Municipal sewage is first separated into degradable and non-degradable waste to optimize the treatment process and enhance environmental protection. Degradable waste, primarily organic matter, can be processed through biological treatment methods like anaerobic digestion, which reduces pollution and generates biogas. Non-degradable waste, such as plastics and metals, requires different handling and disposal methods to prevent contamination of the treatment system and to facilitate recycling or safe disposal. This separation improves efficiency, reduces costs, and minimizes the environmental impact of sewage management.