Onsite/decentralized wastewater treatment systems (so-called ‘septic systems’) are designed for collection, treatment and dispersal/reuse of wastewater from individual homes, clusters of homes, isolated communities, industries or institutional facilities at or near the point of waste generation. Wastewater first undergoes treatment to remove suspended solids and some nutrients and pathogens. The partially treated effluent is then applied to subsurface soil where final polishing occurs prior to dispersal back into the hydrologic cycle. The soil has tremendous capacity to renovate wastewater. However, unless systems are properly designed, sited, installed, maintained, and used, the dispersed effluent may adversely affect surface and groundwater quality. Even properly functioning systems contribute a certain nutrient load (nitrogen and phosphorus) to our ground- and surface waters.