A septic tank is an underwater sedimentation tank used for waste water treatment through the process of biological decomposition and drainage. A septic tank system has a relatively simple design. It is an underground watertight container (mostly rectangular or round) made of fiber glass, plastic or concrete.

For homes that have poor drainage or are not connected to the mains sewage network septic tanks allow a safe disposal of wastewater.

A septic tank will digest organic matter and separate float able matter (e.g., oils and grease) and solids from the wastewater.

Some of the factors that might contribute to septic tank odors near the tank are ineffective digestion in the tank, a septic tank that is full and due for pumping, or loose septic tank covers that are causing the leaking of septic odor. Sulfate-reducing bacteria are also associated with septic odors, specifically hydrogen sulfide. Sulfate-reducing bacteria are naturally present in most septic tanks. These bacteria obtain energy through the oxidation of organic compounds, and they do this as they reduce sulfate to hydrogen sulfide hence their name, sulfate-reducing bacteria.