What is the main function of a septic drain field within an OSSF?

The main function of a septic drain field within an On-Site Sewage Facility (OSSF) is to treat wastewater through soil filtration. When effluent is released from the septic tank, it enters the drain field, where it is distributed into a series of perforated pipes buried in gravel or sand. This setup allows wastewater to percolate through the soil, which acts as a natural filter.

As the effluent moves through the soil layers, various biological, chemical, and physical processes take place. Soil microorganisms break down organic matter, effectively treating the wastewater before it reaches the groundwater or surrounding areas. The treatment process also helps to remove pathogens, nutrients, and contaminants, ensuring that the effluent is sufficiently purified.

While the separation of solids from liquids is a critical function of the septic tank itself, and backup storage for effluent and flood prevention are important considerations in overall system design, the primary role of the drain field is clearly focused on the soil treatment aspect of wastewater management.