Renovation/Restoration of Subsurface Wastewater Infiltration Systems (SWIS)

The subsurface wastewater infiltration system (SWIS) receives the effluent pretreated in the septic tank and purifies it through biological, physical, and chemical reactions as it passes through the unsaturated soil to the ground water. An important component of the infiltration system is the biomat, a layer of organic and inorganic material and bacteria that forms at the interface between the trench and the surrounding soil. The biomat enhances treatment efficiency because it usually slows down the movement of the effluent, provides the flora and fauna necessary to biologically decompose wastes, and enhances the physical and chemical removal of very small particles of matter in the wastewater. Permeable soil textures and structures are required to support these processes.