What is the primary biological process that occurs in a septic tank?

The primary biological process that occurs in a septic tank is anaerobic digestion. This process takes place in the absence of oxygen and involves microorganisms breaking down organic matter found in wastewater, such as solids from human waste and food particles. The anaerobic bacteria thrive in the septic tank environment, where they help decompose the organic material, converting it into simpler compounds such as carbon dioxide, methane, and sludge.

This process is critical for reducing the volume of waste and minimizing the environmental impact of the effluent, which is eventually released into a drain field for further treatment and absorption into the soil. The effectiveness of anaerobic digestion in a septic tank contributes to the tank's ability to handle wastewater treatment efficiently, making it integral to the system's function.