Section 3 How A Septic System Functions

How A Septic System Treats Wastewater

septic-tank-pumping-diagramA typical septic system consists of four main components:  the sewer pipe from the home, a septic tank, a leach field or seepage pit, and the soil. An underground pipe collects the wastewater discharged from the home’s plumbing and connects to the septic tank inlet. The septic tank is typically made of concrete, fiberglass, or polyethylene, is buried, and is watertight. Wastewater entering the septic tank is collected and held long enough to allow solids to settle, forming a sludge layer on the bottom of the tank. Oil and grease separate, forming a scum layer that floats. The remainder of the wastewater, or effluent, forms a layer between the sludge and scum. Anaerobic bacteria, or bacteria that do not require air, work to decompose the solid waste in the septic tank. The effluent exits through a separate, T-shaped pipe that leads to the leach field. The design of the exit pipe prevents sludge and scum from leaving the tank. Leach lines are installed in gravel-filled trenches or seepage pits.  These trenches/ pits must be at least five feet above seasonal high groundwater levels to ensure adequate treatment. Perforated pipes are placed in trenches in the leach field to allow for equal effluent distribution. Microorganisms in the soil aid in removing harmful bacteria, nutrients, and viruses from the effluent.