Concrete septic tanksEquipment for treating feces and filtering sedimentation. The principle is that the solid matter decomposes at the bottom of the pool, while the hydrated matter on top flows into the pipes and away, preventing pipe blockages, and allowing sufficient time for the solid matter (feces and other waste) to hydrolyze. Septic tank refers to a small treatment structure that separates and sedimentates domestic wastewater and anaerobically digests sludge.