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.
Effluent sewer
Another problem area is a place where there are many homes or businesses at or near the lowest elevation in the area, such as sea level for a coastal city. Typically, waste is pumped uphill under low pressure to the main sewer line in such situations, either after it has been through a septic tank or after it has been ground up into a slurry by a grinder. Grinding can be done when the waste of many homes or businesses is combined or smaller grinders can be installed at each home or business. A disadvantage of using grinders is that they require electricity, and a disadvantage of using septic tanks is that they require solid waste buildup to be removed every one to three years, depending on the size of the tank and the number of people using the system.