Hello, onsite wastewater treatment systems (septic systems) can be designed for various size buildings - homes, school, churches, restaurants, nursing homes, and strip malls, etc. The technology has advanced greatly in the last two decades to include aerobic treatment units (ATU) or Best Available Technology (BAT) equaling or surpassing wastewater treatment plants with a good soil dispersal area or drainfield. The size of a home system is based on either number of people or bedrooms. For example, in Maryland a system is designed to process 150 gallons/day/bedroom. A home with 4 bedrooms is designed to process 600 gallons/day and a 12 bedroom home for 1,800 gallons per day. The larger the system, the larger the septic tank or BAT unit and the larger the soil dispersal area. Systems for food operations are designed differently from household wastewater due the difference in composition. essentially, onsite systems can be designed for specific building types and sizes.