What is the function of a leach field?

The leach field, also known as the drain field, plays a critical role in the on-site sewage treatment process by providing a final treatment process for effluent that comes from a septic tank. After the solids are settled out and initial bacterial treatment occurs in the septic tank, the liquid effluent that is expelled is often still loaded with pathogens and nutrients.

The leach field is designed to allow this treated effluent to be dispersed into the surrounding soil where it undergoes further natural filtration and treatment. The soil acts as a natural barrier that helps to remove contaminants and pathogens through physical filtration, chemical reactions, and biological processes involving soil microorganisms. This process is vital in ensuring that the effluent is sufficiently treated before it potentially re-enters the groundwater supply or nearby surface waters.

The other options do not accurately represent the purpose of a leach field. While all types of wastewater storage and treatment are important in wastewater management, that is not the primary function of a leach field. Options discussing pre-treatment or collecting runoff do not align with the specific role that a leach field plays in the overall sewage treatment process.