What is the primary treatment unit in an onsite wastewater system?

The primary treatment unit in an onsite wastewater system is a septic tank that processes raw domestic wastewater. This system is designed specifically to handle the waste generated from households, including human sewage and other domestic effluents. The septic tank works by allowing solids to settle at the bottom, forming sludge, while grease and lighter particles float to the surface, creating a scum layer. The wastewater that remains in the middle layer is allowed to flow to the drain field, where it undergoes further natural treatment as it percolates through the soil.

This process is vital for ensuring that harmful pathogens and pollutants are broken down and filtered out before the wastewater reenters the environment. The importance of the septic tank as a primary treatment unit cannot be overstated, as it serves as the first line of defense in the management of household wastewater, ensuring a safe and effective method for disposal or absorption into the ground.