What is one reason why septic tanks are buried underground?

One reason why septic tanks are buried underground is to reduce temperature variations. This is significant because maintaining a stable temperature is vital for the biological processes that break down waste within the septic tank. When buried, the surrounding soil helps insulate the tank, lessening the impact of environmental temperature changes and providing a more stable habitat for the microorganisms that digest the waste. These microorganisms function best within a certain temperature range; thus, keeping the tank underground supports optimal conditions for the decay process to occur efficiently.