Why do rural areas often use subsurface wastewater disposal?

In rural and sparsely populated areas, subsurface wastewater disposal is primarily used because it is not economically feasible to construct centralized sewage collection systems and treatment plants. Instead, these areas rely on on-site systems, such as septic tanks and absorption fields, which provide effective, long-term, and low-cost solutions for individual homes.1

These systems function by using a septic tank for primary sedimentation, followed by the percolation of effluent through soil. As the wastewater moves through the ground, it undergoes physical and biological purification before reaching the water table. The success of this method depends on the soil's permeability, which must be sufficient to allow for treatment without contaminating groundwater. When soil conditions are unfavorable, alternative methods like mound systems or small-diameter gravity sewers may be employed to maintain public health standards.12