Septic tank
A septic tank is an underground chamber made of concrete, fiberglass or plastic through which domestic wastewater (sewage) flows for basic treatment. Settling and anaerobic processes reduce solids and organics, but the treatment efficiency is only moderate (referred to as "primary treatment"). Septic tank systems are a type of simple onsite sewage facility (OSSF). They can be used in areas that are not connected to a sewerage system, such as rural areas. The treated liquid effluent is commonly disposed in a septic drain field which provides further treatment. However, groundwater pollution may occur and can be a problem.
Grease trap
The second most common type of interceptor is the large in-ground tank, which is usually . These units are constructed of concrete, fiberglass or steel. They have greater grease and solid storage capacities for high-flow applications such as a restaurant or hospital store. They are commonly called gravity interceptors. Interceptors require a retention time of 30 minutes to allow the fats, oils, grease and food solids to settle in the tank. As more waste water enters the tank, the grease-free water is pushed out of the tank. The rotting brown grease inside a grease trap or grease interceptor must be pumped out on a scheduled basis. The brown grease is not recycled and goes to landfill. On average of brown grease goes to landfill annually from each restaurant.